ATMR Altimar Acquisition Corp II

As filed with the United States Securities and Exchange Commission on May 22, 2023

Registration No. 333-262194

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-3

AMENDMENT NO. 1 TO POST-EFFECTIVE AMENDMENT NO. 2 TO REGISTRATION STATEMENT NO. 333-262194

UNDER

THE SECURITIES ACT OF 1933

1050 Walnut Ridge Drive

Hartland, WI 53029

Telephone: (262) 367-8254

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Ryan Martin

Chief Executive Officer

Fathom Digital Manufacturing Corporation

1050 Walnut Ridge Drive

Hartland, WI 53029

Telephone: (262) 367-8254

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies of all communications, including communications sent to agent for service, should be sent to:

Steven J. Gavin

Matthew F. Bergmann

James R. Brown

Winston & Strawn LLP

35 West Wacker Drive Chicago, Illinois 60601

(312) 558-5600

Approximate date of commencement of proposed sale to the public: From time to time after this Registration Statement becomes effective.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box:  ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box:  ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment filed pursuant to Rule 462(e) under the Securities Act, check the following box:  ☐

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box:  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until this registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE AND STATEMENT PURSUANT TO RULE 429

Fathom Digital Manufacturing Corporation (the “Company”) is filing a single prospectus as part of the Registration Statements (as defined below), pursuant to Rule 429 under the Securities Act of 1933, as amended (the “Securities Act”). On January 14, 2022, the Company filed a registration statement on Form S-1 (Registration No. 333-262189), as amended on January 27, 2022, which was subsequently declared effective by the U.S. Securities and Exchange Commission (the “SEC”) on January 28, 2022 (the “First Registration Statement”). Also on January 14, 2022, the Company filed another registration statement on Form S-1 (Registration No. 333-262194), as amended on January 27, 2022, which was subsequently declared effective by the SEC on January 28, 2022 (the “Later Registration Statement” and, together with the First Registration Statement, the “Registration Statements”).

Pursuant to Rule 429 under the Securities Act, this post-effective amendment to the Later Registration Statement (this “Post-Effective Amendment”) will act, upon effectiveness, as a post-effective amendment to both Registration Statements, and is being filed by the Company to convert the Registration Statements on Form S-1 into registration statements on Form S-3. No additional securities are being registered under this Post-Effective Amendment. All applicable registration fees were paid at the time of the original filings of the Registration Statements.

The information in this preliminary prospectus is not complete and may be changed. The Common Stock underlying the Warrants may not be issued, and the Selling Securityholders may not sell these securities, until the registration statement filed with the U.S. Securities and Exchange Commission becomes effective. This preliminary prospectus is not an offer to sell these securities and does not constitute the solicitation of an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED MAY 22, 2023

PRELIMINARY PROSPECTUS

52,423,250 SHARES OF CLASS A COMMON STOCK

9,900,000 WARRANTS TO PURCHASE SHARES OF CLASS A COMMON STOCK

18,525,000 SHARES OF CLASS A COMMON STOCK UNDERLYING WARRANTS TO PURCHASE CLASS A COMMON STOCK AND

90,570,234 SHARES OF CLASS A COMMON STOCK UNDERLYING CLASS B COMMON STOCK

FATHOM DIGITAL MANUFACTURING CORPORATION

This prospectus relates to the resale from time to time by the Selling Securityholders named in this prospectus or their permitted transferees (collectively, the “Selling Securityholders”) of: (i) up to 36,661,014 shares of Class A common stock, par value $0.0001 per share (the “Class A common stock”), issued to certain of the Legacy Fathom Owners in connection with the closing of the Business Combination (as defined herein), (ii) up to 4,770,000 shares of Class A common stock held by Altimar Sponsor II, LLC (the “Sponsor”) and the other Altimar II Founders following the closing of the Business Combination, (iii) up to 2,724,736 Earnout Shares issued to certain Legacy Fathom Owners and (iv) up to 1,267,500 Sponsor Earnout Shares. This prospectus also covers the (a) the resale of up to 9,900,000 Private Placement Warrants to purchase shares of Class A common stock held by the Sponsor, (b) the resale of up to 9,900,000 shares of Class A common stock issuable upon the exercise of the Private Placement Warrants by the Sponsor, (c) the issuance by us of up to 18,525,000 shares of Class A common stock upon the exercise of outstanding Public Warrants and Private Placement Warrants to purchase shares of Class A common stock and (d) the resale by certain of the Legacy Fathom Owners of up to 90,570,234 shares of Class A common stock issuable upon the exchange of New Fathom Units (together with a corresponding number of shares of Class B common stock) held by such Legacy Fathom Owners (including 6,275,264 Earnout Shares presently represented in the form of unvested New Fathom Units). Capitalized terms used but not otherwise defined herein have the meanings given to such terms in the section of this prospectus entitled “Selected Definitions.”

This prospectus also relates to the offer and resale from time to time by certain of the Selling Securityholders named in this prospectus of up to 7,000,000 shares (the “PIPE Shares”) of the Class A common stock which were issued to them in private placements immediately prior to the consummation of the Business Combination.

The Sponsor originally purchased 8,625,000 of our Class B ordinary shares for and aggregate price of $25,000, or approximately $0.003 per share (the “Founder Shares”). On January 28, 2021, our sponsor transferred 25,000 of the Founder Shares to each of our then director nominees, resulting in the Sponsor holding 8,450,000 Founder Shares. On November 16, 2021, the Sponsor and our then directors forfeited and aggregate of 2,587,500 of the Founder Shares, resulting in them holding an aggregate of 6,037,500 Founder Shares. The Founder Shares automatically converted into shares of our Class A common stock at the time of the Closing of the Business Combination, with 1,267,500 of such shares comprising the Sponsor Earnout Shares. In addition, the Sponsor originally purchased the Private Placement Warrants in a private offering at the time of the Altimar II IPO for an aggregate purchase price of $9,900,000, or $1.00 per Private Placement Warrant. The PIPE Shares were purchased by the applicable Selling Securityholders at a price of $10.00 per share. The purchase price of the 36,661,104 shares of Class A common stock issued to certain of the Legacy Fathom Owners and of the 90,570,234 New Fathom Units (which are exchangeable on a one-for-one basis for shares of our Class A common stock) issued to certain other of the Legacy Fathom Owners is unknown. Investors in the Altimar II IPO paid $10.00 per unit, with units consisting of one Altimar II Class A ordinary share and one-fourth of a Public Warrant to purchase an Altimar II Class A ordinary share. The Public Warrants and the Private Placement Warrants automatically converted into the right to purchase shares of our Class A common stock at the time of the closing of the Business Combination. The Selling Securityholders may offer, sell or distribute all or a portion of the shares of Class A common stock and Private Placement Warrants registered for resale hereby publicly or through private transactions at prevailing market prices or at negotiated prices.

We provide more information about how the Selling Securityholders may sell their securities in the section of this prospectus entitled “Plan of Distribution.”

We will receive the proceeds from any exercise of Warrants for cash, but not from the resale of the shares of Class A common stock or Private Placement Warrants by the Selling Securityholders. We could receive up to an aggregate of approximately $213.0 million from the exercise of the Warrants (and the related issuance by us of shares of Class A common stock underlying the Warrants), assuming the exercise in full of all 18,525,000 Warrants for cash. We expect to use the net proceeds from the exercise of the Warrants, if any, for general corporate purposes. We will have broad discretion over the use of proceeds from the exercise of the Warrants. There is no assurance that the holders of the Warrants will elect to exercise any or all of such Warrants. To the extent that the Warrants are exercised on a “cashless basis,” the amount of cash we would receive from the exercise of the Warrants will decrease. The exercise price of the Warrants is $11.50 per share. The likelihood that the Selling Securityholders will exercise their Warrants, and therefore the amount of cash proceeds that we could receive, is dependent upon the market price of our Class A common stock. On May 19, 2023, the closing price of our Class A common stock was $0.5191 per share. If the market price of our Class A common stock continues to be less than the exercise price, it is unlikely that holders will exercise the Warrants, and therefore unlikely that we will receive any proceeds from the exercise of these warrants in the near future, or at all.

As discussed under “Risk Factors,” significant sales of shares of Class A common stock pursuant to the registration statement of which this prospectus forms a part may have a negative pressure on the public trading price of our Class A common stock.

We will pay certain offering fees and expenses in connection with the registration for resale of the Class A common stock and Private Placement Warrants covered by this prospectus. The Selling Securityholders will bear all commissions and discounts, if any, attributable to their respective sales of the Class A common stock and Private Placement Warrants.

You should read this prospectus and any prospectus supplement or amendment carefully before you invest in our Class A common stock or Warrants.

Our Class A common stock is currently listed on the New York Stock Exchange (the “NYSE”) and trades under the symbol “FATH.” Our Public Warrants are currently listed on the NYSE and trade under the symbol “FATH.WS.” On May 19, 2023, the closing sale price of our common stock was $0.5191 per share and the closing price of our Public Warrants was $0.0415 per Public Warrant.

We are an “emerging growth company” and a “smaller reporting company” as those terms are defined under applicable federal securities laws, and as such, are subject to certain reduced public company reporting requirements.

INVESTING IN OUR SECURITIES INVOLVES RISKS THAT ARE REFERRED TO IN THE “RISK FACTORS” SECTION APPEARING ON PAGE 9 OF THIS PROSPECTUS.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued or resold under this prospectus or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is May     , 2023.

You should rely only on the information contained in this prospectus. No one has been authorized to provide you with information that is different from that contained in this prospectus. This prospectus is dated as of the date set forth on the cover hereof. You should not assume that the information contained in this prospectus is accurate as of any date other than that date.

For investors outside the United States: We have taken no actions that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. You are required to inform yourselves about and to observe any restrictions relating to this offering and the distribution of this prospectus.

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the SEC using the “shelf” registration process. Under this shelf registration process, the Selling Securityholders may, from time to time, offer and sell the Class A common stock and Private Placement Warrants offered by them described in this prospectus. We will receive the proceeds from any exercise of Warrants for cash, but will not receive any proceeds from the resale of Class A common stock or Private Placement Warrants by the Selling Securityholders.

Neither we nor the Selling Securityholders have authorized anyone to provide you with any information or to make any representations other than those contained in this prospectus or any applicable prospectus supplement or any free writing prospectuses prepared by or on behalf of us or to which we have referred you. Neither we nor the Selling Securityholders take responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. Neither we nor the Selling Securityholders will make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted.

We may also provide a prospectus supplement or post-effective amendment to the registration statement to add information to, or update or change information contained in, this prospectus. You should read both this prospectus and any applicable prospectus supplement or post-effective amendment to the registration statement together with the additional information to which we refer you in the sections of this prospectus entitled “Where You Can Find More Information” and “Information Incorporated by Reference.”

No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus. This prospectus is not an offer to sell securities, and it is not a solicitation of an offer to buy securities, in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus or any prospectus supplement is accurate only as of the date on the front of those documents, regardless of the time of delivery of this prospectus or any applicable prospectus supplement, or any sale of a security. Our business, financial condition, results of operations and prospects may have changed since those dates.

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described in this prospectus under the section entitled “Where You Can Find More Information.”

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SELECTED DEFINITIONS

When used in this Prospectus, unless the context otherwise requires:

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We disclose certain financial measures in this prospectus that are calculated and presented using methodologies other than in accordance with GAAP. We believe that providing these performance measures on a supplemental basis to our GAAP results is helpful to stockholders in assessing the overall performance of Fathom’s business. These financial measures should not be considered as a substitute for similar financial measures calculated in accordance with GAAP, if available. We present these measures to provide a more complete understanding of our performance as our management measures it. In addition, we caution readers that these non-GAAP financial measures may not be comparable to similarly titled measures used by other companies.

Amounts and percentages throughout this prospectus may reflect rounding adjustments and consequently totals may not appear to sum.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

Certain statements made in this prospectus are “forward looking statements.” Statements regarding our expectations regarding the business are “forward looking statements.” In addition, words such as “estimates,” “projected,” “expects,” “estimated,” “anticipates,” “forecasts,” “plans,” “intends,” “believes,” “seeks,” “may,” “will,” “would,” “future,” “propose,” “target,” “goal,” “objective,” “outlook” and variations of these words or similar expressions (or the negative versions of such words or expressions) are intended to identify forward-looking statements. The forward-looking statements contained in this prospectus and in our periodic filings are not guarantees of future performance, conditions or results and are based on our current expectations and beliefs concerning future developments and their potential effects on us. There can be no assurance that future developments affecting us will be those that we have anticipated. These forward-looking statements involve a number of risks, uncertainties (some of which are beyond our control) or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements. These risks and uncertainties include, but are not limited to, those factors referred to in the section entitled “Risk Factors.” Should one or more of these risks or uncertainties materialize, or should any of our assumptions prove incorrect, actual results may vary in material respects from those projected in these forward-looking statements. We may face additional risks and uncertainties that are not presently known to us, or that we deem to be immaterial, which may also impair our business, financial condition or prospects. We undertake no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required under applicable securities laws.

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RISK FACTORS

Investing in our securities involves risks. Before you make a decision to buy our securities, in addition to the risks and uncertainties discussed above under “Cautionary Note Regarding Forward-Looking Statements” and the risk factors described below, you should carefully consider the specific risks incorporated by reference in this prospectus to our most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, and all other information contained or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in any applicable prospectus supplement and any applicable free writing prospectus before acquiring any such securities. If any of these risks actually occur, it may materially harm our business, financial condition, liquidity and results of operations. As a result, the market price of our securities could decline, and you could lose all or part of your investment. Additionally, the risk factors described below and the risks and uncertainties incorporated by reference in this prospectus or any prospectus supplement are not the only risks and uncertainties that we face. Additional risks and uncertainties not presently known to us or that we currently believe to be immaterial may become material and adversely affect our business.

Sales of shares of our Class A common stock pursuant to the registration statement of which this prospectus forms a part may have negative pressure on the public trading price of our Class A common stock.

The Selling Securityholders will determine the timing, pricing and rate at which they sell the shares registered for resale on the registration statement of which this prospectus forms a part into the public market. Significant sales of shares of Class A common stock pursuant to the registration statement of which this prospectus forms a part may have negative pressure on the public trading price of our Class A common stock. The shares being registered for resale currently represent approximately 96.6% of the total number of shares outstanding, based on the number of shares of Class A common stock outstanding as of May 18, 2023 (assuming the exchange of all of our outstanding shares of Class B common stock and related New Fathom Units, vesting of all Earnout Shares and Sponsor Earnout Shares and the issuance of the 9,900,000 shares of Class A common stock issuable upon exercise of the Private Placement Warrants). Also, even though the current trading price is significantly below the Company’s initial public offering price (in February 2021 Altimar II IPO) of approximately $10.00 per share, based on the closing price of the Class A common stock on May 19, 2023, certain private investors may have an incentive to sell their shares, because they will still profit on sales due to the lower prices at which they purchased their shares as compared to the public investors. The holders of these shares will be able to sell all or material portion of their shares for so long as the registration statement of which this prospectus forms a part is available for use.

While certain Selling Securityholders may experience a positive rate of return based on the current trading price of our Class A common stock, public securityholders may not experience a similar rate of return on the securities they purchased due to differences in the purchase prices and the current trading price of our Class A common stock. Based on the closing price of the Class A common stock on May 19, 2023, which was $0.5191 per share, and assuming the resale by the Selling Securityholders of all 142,993,484 shares of Class A common stock being registered for resale on the registration statement of which this prospectus forms a part, the Selling Securityholders could earn approximately $74.2 million in aggregate proceeds from the resale of such shares. The PIPE Shares were purchased for $10.00 per share and, therefore, based on the closing price of the Class A common stock on May 19, 2023, such Selling Holders would not earn any profit from the resale of such shares. The 4,770,000 Founder Shares (excluding the unvested Sponsor Earnout Shares) were purchased for approximately $0.003 per share, and, therefore, based on the closing price of the Class A common stock on May 19, 2023, such Selling Securityholders would earn an aggregate profit of $2.5 million from the resale of such shares. The 9,900,000 shares of Class A common stock issuable upon exercise of the Private Placement Warrants will be issued at a price of $11.50 per share (the exercise price of the Private Placement Warrants) and, therefore, based on the closing price of the Class A common stock on May 19, 2023, such Selling Securityholder would not earn any profit from the resale of such shares. The purchase price of the shares Class A common stock

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and New Fathom Units exchangeable for shares of Class A common stock issued to the Legacy Fathom Owners in the Business Combination is unknown and, therefore, the potential profit (if any) such Selling Securityholders would earn from the resale of all such shares is unknown.

Future sales of Fathom Class A common stock, or the perception of such future sales, by us or our stockholders in the public market could make it more difficult for us to raise additional equity capital.

As discussed in the immediately preceding risk factor, the sale of shares of our Class A common stock in the public market, or the perception that such sales could occur, could harm the prevailing market price of the Class A common stock. As a result, these sales, or the possibility that these sales may occur, also might make it more difficult for us to sell equity securities in the future at a time and at a price that we deem appropriate.

Our Warrants are presently “out of the money” and there is no guarantee that our Warrants will be in the money before they expire, and they may expire worthless.

As of the date of this prospectus, we have 18,525,000 Warrants outstanding including the 9,900,000 Private Placement Warrants. The exercise price for our Warrants is $11.50 per share, which will expire if unexercised on December 23, 2026. The likelihood that the holders will exercise their Warrants, and therefore the amount of cash proceeds that we could receive, is dependent upon the market price of our Class A common stock. On May 19, 2023, the closing price of our Class A common stock was $0.5191 per share. If the market price of our Class A common stock continues to be less than the exercise price of the Warrants, it is unlikely that holders will exercise the Warrants, and therefore unlikely that we will receive any proceeds from the exercise of these warrants in the near future, or at all.

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USE OF PROCEEDS

All of the shares of our Class A common stock and Private Placement Warrants offered by the Selling Securityholders pursuant to this prospectus will be sold by the Selling Securityholders for their respective accounts. We will not receive any proceeds from the sale of the shares or Private Placement Warrants by the Selling Securityholders.

We could receive up to an aggregate of approximately $213.0 million from the exercise of the Warrants (and the related issuance by us of shares of Class A common stock underlying the Warrants), assuming the exercise in full of all 18,525,000 Warrants for cash. We expect to use the net proceeds from the exercise of the Warrants, if any, for general corporate purposes. We will have broad discretion over the use of proceeds from the exercise of the Warrants. There is no assurance that the holders of the Warrants will elect to exercise any or all of such Warrants. To the extent that the Warrants are exercised on a “cashless basis,” the amount of cash we would receive from the exercise of the Warrants will decrease.

The exercise price of the Warrants is $11.50 per share. The likelihood that the Selling Securityholders will exercise their Warrants, and therefore the amount of cash proceeds that we could receive, is dependent upon the market price of our Class A common stock. On May 19, 2023, the closing price of our Class A common stock was $0.5191 per share. If the market price of our Class A common stock continues to be less than the exercise price, it is unlikely that holders will exercise the Warrants, and therefore unlikely that we will receive any proceeds from the exercise of these warrants in the near future, or at all.

The Selling Securityholders will pay all incremental selling expenses relating to the sale of their securities, including underwriters’ or agents’ commissions and discounts, brokerage fees, underwriter marketing costs and legal counsel representing the Selling Securityholders, except that we will pay the reasonable fees and expenses of one legal counsel for the Selling Securityholders, in the event of an underwritten offering of their securities. We will bear all other costs, fees and expenses incurred in effecting the registration of the shares covered by this prospectus, including, without limitation, all registration and filing fees, printing and delivery fees, NYSE listing fees and fees and expenses of our counsel and our independent registered public accounting firm.

DETERMINATION OF OFFERING PRICE

We cannot currently determine the price or prices at which shares of our Class A common stock or Private Placement Warrants may be sold by the Selling Securityholders under this prospectus.

MARKET PRICE OF OUR COMMON STOCK AND WARRANTS AND DIVIDEND INFORMATION

Market Price of our Common Stock and Public Warrants

Our Class A common stock and Public Warrants are currently listed on NYSE under the symbols “FATH” and “FATH.WS,” respectively. Prior to the consummation of the Business Combination, Altimar II’s Class A ordinary shares and Public Warrants traded on the NYSE under the ticker symbols “ATMR” and “ATMR.WS,” respectively. On May 19, 2023, the closing sale price of our Class A common stock and Public Warrants was $0.5191 and $0.0415, respectively. The Private Placement Warrants are not listed on any Stock exchange and we do not intend to list the Private Placement Warrants on any exchange or stock market. As of May 18, 2023, there were 32 holders of record of Class A common stock, 3 holders of Class B common stock and 2 holders of record of the Company’s Warrants. Such numbers do not include beneficial owners holding our securities through nominee names. Our Class B common stock is not registered and we do not intend to list the Class B common stock on any exchange or stock market.

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Dividend Policy

We have not paid any cash dividends on our common stock to date, and prior to the Business Combination, Altimar II had not paid any dividends on its ordinary shares. The payment of cash dividends in the future will be dependent upon our revenues and earnings, if any, capital requirements and general financial condition, and subject to restrictions contained in the New Credit Agreement. The payment of any cash dividends will be within the discretion of our board of directors. Our ability to declare dividends may be limited by the terms of financing or other agreements entered into by us or our subsidiaries from time to time.

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DILUTION

The Selling Securityholders are offering for resale up to 152,893,484 shares of Class A common stock. The resale of the current outstanding shares of Class A common stock under this prospectus will not dilute the ownership interests of existing stockholders.

DESCRIPTION OF FATHOM SECURITIES

Our authorized capital stock consists of 300,000,000 shares of Class A common stock, par value $0.0001 per share; 180,000,000 shares of Class B common stock, par value $0.0001 per share; 10,000,000 shares of Class C common stock, par value $0.0001 per share; and 10,000,000 shares of preferred stock, par value $0.0001 per share.

As of May 18, 2023, we had (i) 69,690,343 shares of Class A common stock outstanding, (ii) 66,692,781 shares of Class B common stock outstanding, (iii) zero shares of Class C common Stock outstanding and (iv) zero shares of Preferred Stock outstanding.

We have not entered into any forward purchase or other agreements that provide investors with the right to sell back shares to the Company at a fixed price for a given period of time after the Closing of the Business Combination.

The following summary of our securities and our Charter and our Bylaws does not purport to be complete and is qualified in its entirety by reference to the provisions of applicable law and to our Charter, our Bylaws, the Fathom Operating Agreement and the Warrant Agreement which are filed as exhibits to the registration statement of which this prospectus is a part.

Common Stock

Class A common stock

Voting rights. Each holder of Class A common stock is entitled to one vote for each share of Class A common stock held of record by such holder on all matters on which stockholders generally are entitled to vote. Holders of Class A common stock will vote together with the holder of Class B common stock and Class C common stock as a single class on all matters presented to the Company’s stockholders for their vote or approval. Generally, subject to the Investor Rights Agreement and except for certain matters requiring supermajority approval by our Charter as described below under “—Supermajority Approval Requirements,” all matters to be voted on by stockholders must be approved by a majority (or, in the case of election of directors, by a plurality) of the votes entitled to be cast by all stockholders present in person or represented by proxy, voting together as a single class. Stockholders do not have the ability to cumulate votes for the election of directors. Our Charter provides for a classified Board consisting of three classes of approximately equal size, each serving staggered three-year terms. Only one class of directors will be elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms.

Notwithstanding the foregoing, to the fullest extent permitted by law, holders of our common stock, as such, will have no voting power with respect to, and will not be entitled to vote on, any amendment to our Charter (including any certificate of designations relating to any series of preferred stock) that relates solely to the terms of one or more outstanding series of preferred stock, if the holders of such affected series are entitled, either separately or together with the holders of one or more other such series, to vote thereon pursuant to the Proposed Charter (including any certificate of designations relating to any series of preferred stock) or pursuant to the DGCL.

Dividend Rights. Subject to preferences that may be applicable to any outstanding preferred stock, the holders of shares of Class A common stock are entitled to receive ratably such dividends, if any, as may be declared from time to time on our common stock having dividend rights by our Board out of funds legally available therefor.

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Rights upon liquidation. In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company’s affairs, the holders of Class A common stock are entitled to share ratably in all assets remaining after payment of Fathom’s debts and other liabilities, subject to pari passu and prior distribution rights of preferred stock or any class or series of stock having a preference over the Class A common stock, then outstanding, if any.

Other rights. Except as provided in the Investor Rights Agreement (as applicable), the holders of Class A common stock will have no preemptive or conversion rights or other subscription rights. There are no redemption or sinking fund provisions applicable to the Class A common stock. The rights, preferences and privileges of holders of the Class A common stock are subject to those of the holders of any shares of the preferred stock the Company may issue in the future and to the Investor Rights Agreement, as applicable.

Subject to the transfer and exchange restrictions set forth in the Fathom Operating Agreement, holders of New Fathom Units may exchange these units for shares of our Class A common stock, on a one-for-one basis or, at the election of an exchange committee of Fathom OpCo, for cash. When a New Fathom Unit is exchanged, a corresponding share of our Class B common stock, depending on the holder, will automatically be transferred to us and retired for no consideration.

Class B common stock

Voting Rights. Holders of our Class B common stock are entitled to one vote for each share held of record on all matters submitted to a vote of stockholders. Holders of Class B common stock will vote together with holders of Class A common stock and Class C common stock as a single class on all matters presented to Fathom’s stockholders for their vote or approval, except as otherwise required by our Charter and applicable law.

Dividend Rights. Holders of the Class B common stock will not be entitled to dividends in respect of their shares of Class B common stock.

Rights upon liquidation. The holders of shares of Class B common stock, as such, shall not be entitled to receive any assets of Fathom in the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company’s affairs. We refer to the Class B common stock as “vote-only” shares.

Redemption of Class B common stock for Class A common stock. Shares of Class B common stock are redeemable for shares of Class A common stock on the terms and subject to the conditions set forth in the Fathom Operating Agreement. The Company may satisfy its or its affiliates’ obligations in respect of any redemption of shares of Class B common stock under the Fathom Operating Agreement by delivering (either directly or indirectly through an affiliate) to the holder of shares of Class B common stock upon such redemption, in lieu of newly issued shares of Class A common stock, cash in the amount permitted by and provided in the Fathom Operating Agreement or shares of Class A common stock which are held in the treasury of Fathom. All shares of Class A common stock that may be issued upon any such redemption will, upon issuance in accordance with the Fathom Operating Agreement, be validly issued, fully paid and non-assessable. All shares of Class B common stock so redeemed for Class A common stock shall be cancelled.

Other rights. Except as provided in the Investor Rights Agreement (as applicable), the holders of Class B common stock will have no preemptive or other subscription rights. The rights, preferences and privileges of holders of the Class B common stock are subject to those of the holders of any shares of the preferred stock Fathom may issue in the future and to the Investor Rights Agreement, as applicable.

Issuance and Transfer. There will be no further issuances of Class B common stock except in connection with (i) a stock split, stock dividend, reclassification or similar transaction, (ii) an issuance of New Fathom Units or (iii) a Triggering Event occurring with respect to an Earnout Share in the form of a New Fathom Unit. When a New Fathom Unit is exchanged pursuant to the Fathom Operating Agreement, a corresponding share of our

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Class B common stock will automatically be transferred to us and retired for no consideration. Class B common stock is not transferable unless a corresponding number of New Fathom Units are simultaneously transferred to the same person.

Preferred Stock

Our Charter authorizes the Board to establish one or more series of preferred stock in one or more classes or series and to fix the rights, preferences, privileges and related restrictions, including dividend rights, dividend rates, conversion rights, voting rights, the right to elect directors, terms of redemption, redemption prices, liquidation preferences and the number of shares constituting any class or series, or the designation of the class or series, without the approval of our stockholders.

The authority of our Board to issue preferred stock without approval of our stockholders may have the effect of delaying, deferring or preventing a change in control of Fathom and may adversely affect the voting and other rights of the holders of our common stock. The issuance of preferred stock with voting and conversion rights may adversely affect the voting power of the holders of our common stock, including the loss of voting control to others. As a result of these or other factors, the issuance of preferred stock could have an adverse impact on the market price of the Class A common stock. At present, we have no plans to issue any preferred stock.

Authorized but Unissued Capital Stock

Delaware law does not require stockholder approval for any issuance of authorized shares. However, the listing requirements of The New York Stock Exchange, which would apply so long as the Class A common stock remains listed on the New York Stock Exchange, require stockholder approval of certain issuances equal to or exceeding 20% of the then outstanding voting power or then outstanding number of shares of Class A common stock. These additional shares may be used for a variety of corporate purposes, including future public offerings, to raise additional capital or to facilitate acquisitions.

One of the effects of the existence of unissued and unreserved common stock or preferred stock may be to enable our Board to issue shares to persons friendly to current management, which issuance could render more difficult or discourage an attempt to obtain control of our Company by means of a merger, tender offer, proxy contest or otherwise, and thereby protect the continuity of our management and possibly deprive the stockholders of opportunities to sell their shares of common stock at prices higher than prevailing market prices.

Anti-Takeover Effects of Provisions of Delaware Law and our Charter and Bylaws

Certain provisions of our Charter and Bylaws could discourage potential acquisition proposals and could delay or prevent a change in control. These provisions are intended to enhance the likelihood of continuity and stability in the composition of our Board and in the policies formulated by our Board and to discourage certain types of transactions that may involve an actual or threatened change of control. These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal or proxy fight. Such provisions could have the effect of discouraging others from making tender offers for our shares and, as a consequence, they also may inhibit fluctuations in the market price of our Class A common stock that could result from actual or rumored takeover attempts. Such provisions also may have the effect of preventing changes in our management or delaying or preventing a transaction that might benefit you or other minority stockholders.

These provisions include:

No Action by Written Consent; Special Meetings of Stockholders. The DGCL permits stockholder action by written consent unless otherwise provided by our Charter. Our Charter precludes holders of common stock from taking action by written consent. If permitted by the applicable certificate of designation, future series of preferred stock may take action by written consent. Our Charter and Bylaws provide that special meetings of

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stockholders may be called (i) only by the Board or the chairman of the Board pursuant to a written resolution adopted by the affirmative vote of the number of directors equal to a majority of the Board assuming no vacancies or (ii) prior to the date on which the CORE Investors and their affiliates cease to beneficially own in the aggregate (directly or indirectly) at least 25% of the then outstanding Common Stock, by the chairman of the Board at the written request of holders of at least a majority of the then outstanding common stock. Further, any business transacted at any special meeting of stockholders is limited to the purpose or purposes included in the notice may be considered at such special meeting.

Election and Removal of Directors. The DGCL provides that stockholders are not entitled to the right to cumulate votes in the election of directors unless the corporation’s certificate of incorporation provides otherwise. Our Charter does not expressly provide for cumulative voting. Directors may be removed, but only for cause (and subject to the Investor Rights Agreement), upon the affirmative vote of holders of 66-2/3% of the voting power of the outstanding shares of our capital stock entitled to vote generally in the election of directors, voting together as a single class. In addition, the certificate of designation pursuant to which a particular series of preferred stock is issued may provide holders of that series of preferred stock with the right to elect additional directors. In addition, under our Charter, our Board is divided into three classes of directors, each of which will hold office for a three-year term. The existence of a classified Board could delay a successful tender offeror from obtaining majority control of our Board, and the prospect of that delay might deter a potential offeror.

Supermajority Approval Requirements. Our Charter and Bylaws provide that our Board is expressly authorized to make, alter, amend, change, add to, rescind or repeal, in whole or in part, the Bylaws without a stockholder vote in any matter not inconsistent with the laws of the State of Delaware and our Charter. In addition, any amendment, alteration, change, addition, rescission or repeal of the Bylaws by our stockholders will require the affirmative vote of holders of 66-2/3% in voting power of the outstanding shares of our stock entitled to vote on such amendment, alteration, change, addition, rescission or repeal.

The DGCL provides generally that the affirmative vote of a majority of the outstanding shares entitled to vote thereon, voting together as a single class, is required to amend a Delaware corporation’s certificate of incorporation, unless the certificate of incorporation requires a greater percentage. Our Charter provides that the following provisions in the Charter may be amended, altered, repealed or rescinded only by the affirmative vote of the holders of at least 66-2/3% (or, 80%, for the provision indicated below) in voting power of all the then- outstanding shares of stock of Fathom entitled to vote thereon, voting together as a single class:

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The combination of the classification of our Board, the lack of cumulative voting and the supermajority voting requirements will make it more difficult for our existing stockholders to replace our Board as well as for another party to obtain control of us by replacing our Board. Because our Board has the power to retain and discharge our officers, these provisions could also make it more difficult for existing stockholders or another party to effect a change in management.

Authorized but Unissued Shares. The authorized but unissued shares of common stock and preferred stock are available for future issuance without stockholder approval, subject to any limitations imposed by the listing rules of The New York Stock Exchange. The existence of authorized but unissued and unreserved common stock and preferred stock could make more difficult or discourage an attempt to obtain control of us by means of a proxy contest, tender offer, merger or otherwise. See “Description of Fathom’s Capital Stock—Preferred Stock” and “Description of Fathom’s Capital Stock—Authorized but Unissued Capital Stock” above.

Business Combinations with Interested Stockholders. In general, Section 203 of the DGCL, an anti- takeover law, prohibits a publicly held Delaware corporation from engaging in a business combination, such as a merger, with a person or group owning 15% or more of the corporation’s voting stock, which person or group is considered an interested stockholder under the DGCL, for a period of three years following the date the person became an interested stockholder, unless (with certain exceptions) the business combination or the transaction in which the person became an interested stockholder is approved in a prescribed manner.

We have opted out of Section 203 of the DGCL.

Other Limitations on Stockholder Actions. Our Bylaws also impose some procedural requirements on stockholders who wish to:

Under these procedural requirements, in order to bring a proposal before a meeting of stockholders, a stockholder must deliver timely notice of a proposal pertaining to a proper subject for presentation at the meeting to our corporate secretary containing, among other things, the following:

The Bylaws set out the timeliness requirements for delivery of notice.

In order to submit a nomination for our Board, a stockholder must also submit any information with respect to the nominee that we would be required to include in a proxy statement, as well as some other information. If a stockholder fails to follow the required procedures, the stockholder’s proposal or nominee will be ineligible and will not be voted on by our stockholders.

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Limitations on Liability and Indemnification of Officers and Directors

Our Charter and Bylaws provide indemnification for our directors and officers to the fullest extent permitted by the DGCL. We plan to enter into indemnification agreements with each of our directors and executive officers that may, in some cases, be broader than the specific indemnification provisions contained under Delaware law. In addition, as permitted by Delaware law, our Charter includes provisions that eliminate the personal liability of our directors for monetary damages resulting from breaches of certain fiduciary duties as a director. The effect of this provision is to restrict our rights and the rights of our stockholders in derivative suits to recover monetary damages against a director for breach of fiduciary duties as a director, except that a director will be personally liable for:

These provisions may be held not to be enforceable for violations of the federal securities laws of the United States.

Forum Selection

Our Charter provides that unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware will, to the fullest extent permitted by applicable law, be the sole and exclusive forum for:

Our Charter also provides that any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock will be deemed to have notice of, and to have consented to, this forum selection provision. Although we believe these provisions benefit us by providing increased consistency in the application of Delaware law for the specified types of actions and proceedings, the provisions may have the effect of discouraging lawsuits against our directors, officers, employees and agents. The enforceability of similar exclusive forum provisions in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that, in connection with one or more actions or proceedings described above, a court could rule that this provision in our Charter is inapplicable or unenforceable.

Stockholder Registration Rights

Under the terms of the Registration Rights Agreement, Fathom granted to the Legacy Fathom Owners, Sponsor and certain other former Altimar II equityholders customary demand, shelf and piggyback registration rights. Fathom is required to file within thirty days of the Closing a shelf registration statement registering the

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public resale of the shares of common stock of Fathom (“Shelf Registration Statement”), and cause the Shelf Registration Statement to be declared effective as promptly as practicable after the filing thereof and no later than the earlier of (A) 60 calendar days after the filing thereof (or, in the event the SEC reviews and has written comments to the Shelf Registration Statement, the 90th calendar day following the filing thereof) and (B) the 10th business day after the date Fathom is notified (orally or in writing, whichever is earlier) by the SEC that it will not review the Shelf Registration Statement. See “Certain Relationships and Related Party Transactions—Registration Rights Agreement.” The PIPE Investors also have been granted certain, customary registration rights pursuant to the Subscription Agreements.

Warrants

Public Warrants. Each whole Warrant entitles the registered holder to purchase one share of Class A common stock at a price of $11.50 per share, subject to adjustment as discussed below, at any time commencing on the later of one year from the closing of the Altimar II IPO and 30 days after the completion of the Business Combination, which occurred on December 23, 2021, except as discussed in the immediately succeeding paragraph. Pursuant to the Warrant Agreement, a Warrant holder may exercise its Warrants only for a whole number of Class A common stock. This means only a whole Warrant may be exercised at a given time by a Warrant holder. No fractional Warrants will be issued upon separation of the units and only whole Warrants will trade. The Warrants will expire five years after the completion of the Business Combination, at 5:00 p.m., New York City time, which occurred on December 23, 2021, or earlier upon redemption or liquidation.

We will not be obligated to deliver any Class A common stock pursuant to the exercise of a Warrant and will have no obligation to settle such Warrant exercise unless a registration statement under the Securities Act with respect to the Class A common stock underlying the Warrants is then effective and a prospectus relating thereto is current, subject to our satisfying our obligations described below with respect to registration, or a valid exemption from registration is available. No Warrant will be exercisable and we will not be obligated to issue a share of Class A common stock upon exercise of a Warrant unless the Class A common stock issuable upon such Warrant exercise has been registered, qualified or deemed to be exempt under the securities laws of the state of residence of the registered holder of the Warrants. In the event that the conditions in the two immediately preceding sentences are not satisfied with respect to a Warrant, the holder of such Warrant will not be entitled to exercise such Warrant and such Warrant may have no value and expire worthless. In no event will we be required to net cash settle any Warrant. In the event that a registration statement is not effective for the exercised Warrants, the purchaser of a unit containing such Warrant will have paid the full purchase price for the unit solely for the Class A common stock underlying such unit.

We have filed with the SEC registration statements for the registration, under the Securities Act, of the Warrants and the common stock issuable upon exercise of the Warrants, and we will use our commercially reasonable efforts to maintain the effectiveness of such registration statements and a current prospectus relating to those shares of Class A common stock until the Warrants expire or are redeemed, as specified in the Warrant Agreement; provided that if our Class A common stock is at the time of any exercise of a Public Warrant not listed on a national securities exchange such that they satisfy the definition of a “covered security” under Section 18(b)(1) of the Securities Act, we may, at our option, require holders of Public Warrants who exercise their Warrants to do so on a “cashless basis” in accordance with Section 3(a)(9) of the Securities Act and, in the event we so elect, we will not be required to file or maintain in effect a registration statement for the registration, under the Securities Act, of the Class A common stock issuable upon exercise of the Warrants, but we will use our commercially reasonably efforts to register or qualify for sale the shares under applicable blue sky laws to the extent an exemption is not available. If a registration statement covering the Class A common stock issuable upon exercise of the Warrants is not effective by the 60th day after the Closing of the Business Combination, Warrant holders were permitted to, until such time as there was an effective registration statement and during any period when we will have failed to maintain an effective registration statement, exercise Warrants on a “cashless basis” in accordance with Section 3(a)(9) of the Securities Act or another exemption, but we will use our

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commercially reasonably efforts to register or qualify the shares under applicable blue sky laws to the extent an exemption is not available. In such event, each Warrant holder would pay the exercise price by surrendering the Warrants for that number of shares of Class A common stock equal to the lesser of (A) the quotient obtained by dividing (x) the product of the number of shares of Class A common stock underlying the Warrants, multiplied by the excess of the “fair market value” (defined below) over the exercise price of the Warrants by (y) the fair market value and (B) 0.361 per Warrant. The “fair market value” as used in this paragraph shall mean the volume weighted average per share price of the Class A common stock for the 10 trading days ending on the trading day prior to the date on which the notice of exercise is received by the Warrant Agent.

Redemption of Warrants when the price per share of Class A common stock equals or exceeds $18.00

Once the Warrants become exercisable, we may redeem the outstanding Warrants (except as described herein with respect to the Private Placement Warrants):

We will not redeem the Warrants as described above unless a registration statement under the Securities Act covering the issuance of the Class A common stock issuable upon exercise of the Warrants is then effective and a current prospectus relating to those shares of Class A common stock is available throughout the 30-day redemption period. If and when the Warrants become redeemable by us, we may exercise our redemption right even if we are unable to register or qualify the underlying securities for sale under all applicable state securities laws.

If we call the Warrants for redemption as described above, our management will have the option to require all holders that wish to exercise Warrants to do so on a “cashless basis.” In determining whether to require all holders to exercise their Warrants on a “cashless basis,” our management will consider, among other factors, our cash position, the number of Warrants that are outstanding and the dilutive effect on our shareholders of issuing the maximum number of shares of Class A common stock issuable upon the exercise of our Warrants. In such event, each holder would pay the exercise price by surrendering the Warrants for that number of shares of Class A common stock equal to the lesser of (A) the quotient obtained by dividing (x) the product of the number of shares of Class A common stock underlying the Warrants, multiplied by the excess of the “fair market value” of our Class A common stock over the exercise price of the Warrants by (y) the fair market value and (B) 0.361 per Warrant.

We have established the last of the redemption criterion discussed above to prevent a redemption call unless there is at the time of the call a significant premium to the Warrant exercise price. If the foregoing conditions are satisfied and we issue a notice of redemption of the Warrants, each Warrant holder will be entitled to exercise his, her or its Warrant prior to the scheduled redemption date. Any such exercise would not be done on a “cashless” basis and would require the exercising Warrant holder to pay the exercise price for each Warrant being exercised. However, the price of the Class A common stock may fall below the $18.00 redemption trigger price (as adjusted for adjustments to the number of shares issuable upon exercise or the exercise price of a Warrant as described below under the heading “—Warrants—Public Warrants—Anti-Dilution Adjustments”) as well as the $11.50 (for whole shares) Warrant exercise price after the redemption notice is issued.

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Redemption of Warrants when the price per share of Class A common stock equals or exceeds $10.00

Once the Warrants become exercisable, we may redeem the outstanding Warrants (except as described herein with respect to the Private Placement Warrants):

Beginning on the date the notice of redemption is given until the Warrants are redeemed or exercised, holders may elect to exercise their Warrants on a cashless basis. The numbers in the table below represent the number of shares of Class A common stock that a Warrant holder will receive upon such cashless exercise in connection with a redemption by us pursuant to this redemption feature, based on the “fair market value” of our Class A common stock on the corresponding redemption date (assuming holders elect to exercise their Warrants and such Warrants are not redeemed for $0.10 per Warrant), determined for these purposes and in “—Redemption of Warrants when the price per share of Class A common stock equals or exceeds $18.00” above based on volume weighted average price of our Class A common stock for the 10 trading days ending on the third trading day prior to the date on which the notice of redemption is sent to the holders of Warrants, and the number of months that the corresponding redemption date precedes the expiration date of the Warrants, each as set forth in the table below. We will provide our Warrant holders with the final fair market value no later than one business day after the 10-trading day period described above ends.

The share prices set forth in the column headings of the table below will be adjusted as of any date on which the number of shares issuable upon exercise of a Warrant or the exercise price of a Warrant is adjusted as set forth under the heading “—Anti-Dilution Adjustments” below. If the number of shares issuable upon exercise of a Warrant is adjusted, the adjusted share prices in the column headings will equal the share prices immediately prior to such adjustment, multiplied by a fraction, the numerator of which is the exercise price of the Warrant after such adjustment and the denominator of which is the exercise price of the Warrant immediately prior to such adjustment. In such an event, the number of shares in the table below shall be adjusted by multiplying such share amounts by a fraction, the numerator of which is the number of shares deliverable upon exercise of a Warrant immediately prior to such adjustment and the denominator of which is the number of shares deliverable upon exercise of a Warrant as so adjusted. If the exercise price of a Warrant is adjusted, (a) in the case of an adjustment pursuant to the fifth paragraph under the heading “—Anti-Dilution Adjustments” below, the adjusted share prices in the column headings will equal the unadjusted share price multiplied by a fraction, the numerator of which is the higher of the Market Value and the Newly Issued Price as set forth under the heading “—Anti-Dilution Adjustments” and the denominator of which is $10.00 and (b) in the case of an adjustment pursuant to the second paragraph under the heading “—Anti-Dilution Adjustments” below, the adjusted share prices in the

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column headings will equal the unadjusted share price less the decrease in the exercise price of a Warrant pursuant to such exercise price adjustment.

The exact fair market value and redemption date may not be set forth in the table above, in which case, if the fair market value is between two values in the table or the redemption date is between two redemption dates in the table, the number of shares of Class A common stock to be issued for each Warrant exercised will be determined by a straight-line interpolation between the number of shares set forth for the higher and lower fair market values and the earlier and later redemption dates, as applicable, based on a 365 or 366-day year, as applicable. For example, if the volume weighted average price of our Class A common stock for the 10 trading days ending on the third trading day prior to the date on which the notice of redemption is sent to the holders of the Warrants is $11.00 per share, and at such time there are 57 months until the expiration of the Warrants, holders may choose to, in connection with this redemption feature, exercise their Warrants for 0.277 of a share of Class A common stock for each whole Warrant. For an example where the exact fair market value and redemption date are not as set forth in the table above, if the volume weighted average price of our Class A common stock for the 10 trading days ending on the third trading day prior to the date on which the notice of redemption is sent to the holders of the Warrants is $13.50 per share, and at such time there are 38 months until the expiration of the Warrants, holders may choose to, in connection with this redemption feature, exercise their Warrants for 0.298 of a share of Class A common stock for each whole Warrant. In no event will the Warrants be exercisable on a cashless basis in connection with this redemption feature for more than 0.361 of a share of Class A common stock per Warrant (subject to adjustment). Finally, as reflected in the table above, if the Warrants are out of the money and about to expire, they cannot be exercised on a cashless basis in connection with a redemption by us pursuant to this redemption feature, since they will not be exercisable for any Class A common stock.

This redemption feature differs from the typical Warrant redemption features used in many other blank check offerings, which typically only provide for a redemption of Warrants for cash (other than the Private Placement Warrants) when the trading price for the Class A common stock exceeds $18.00 per share for a specified period of time. This redemption feature is structured to allow for all of the outstanding Warrants to be

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redeemed when the Class A common stock is trading at or above $10.00 per public share, which may be at a time when the trading price of our Class A common stock is below the exercise price of the Warrants. We have established this redemption feature to provide us with the flexibility to redeem the Warrants without the Warrants having to reach the $18.00 per share threshold set forth above under “—Redemption of Warrants when the price per share of Class A common stock equals or exceeds $18.00.” Holders choosing to exercise their Warrants in connection with a redemption pursuant to this feature will, in effect, receive a number of shares for their Warrants based on an option pricing model with a fixed volatility input as of this prospectus. This redemption right provides us with an additional mechanism by which to redeem all of the outstanding Warrants, and therefore have certainty as to our capital structure as the Warrants would no longer be outstanding and would have been exercised or redeemed. We will be required to pay the applicable redemption price to Warrant holders if we choose to exercise this redemption right and it will allow us to quickly proceed with a redemption of the Warrants if we determine it is in our best interest to do so. As such, we would redeem the Warrants in this manner when we believe it is in our best interest to update our capital structure to remove the Warrants and pay the redemption price to the Warrant holders.

As stated above, we can redeem the Warrants when the Class A common stock is trading at a price starting at $10.00, which is below the exercise price of $11.50, because it will provide certainty with respect to our capital structure and cash position while providing Warrant holders with the opportunity to exercise their Warrants on a cashless basis for the applicable number of shares. If we choose to redeem the Warrants when the Class A common stock is trading at a price below the exercise price of the Warrants, this could result in the Warrant holders receiving fewer shares of Class A common stock than they would have received if they had chosen to wait to exercise their Warrants for Class A common stock if and when such Class A common stock was trading at a price higher than the exercise price of $11.50.

No fractional shares of Class A common stock will be issued upon exercise. If, upon exercise, a holder would be entitled to receive a fractional interest in a share, we will round down to the nearest whole number of the number of shares of Class A common stock to be issued to the holder. If, at the time of redemption, the Warrants are exercisable for a security other than the Class A common stock pursuant to the Warrant Agreement, the Warrants may be exercised for such security. At such time as the Warrants become exercisable for a security other than the Class A common stock, the Company will use its commercially reasonable efforts to register under the Securities Act the security issuable upon the exercise of the Warrants.

Redemption Procedures

A holder of a Warrant may notify us in writing in the event it elects to be subject to a requirement that such holder will not have the right to exercise such Warrant, to the extent that after giving effect to such exercise, such person (together with such person’s affiliates), to the Warrant Agent’s actual knowledge, would beneficially own in excess of 9.8% (or such other amount as a holder may specify) of the Class A common stock issued and outstanding immediately after giving effect to such exercise.

Anti-Dilution Adjustments

If the number of outstanding shares of Class A common stock is increased by a capitalization or share dividend payable in Class A common stock, or by a split-up of shares or other similar event, then, on the effective date of such capitalization or share dividend, split-up or similar event, the number of shares of Class A common stock issuable on exercise of each Warrant will be increased in proportion to such increase in the outstanding shares of Class A common stock. A rights offering made to all or substantially all holders of Class A common stock entitling holders to purchase Class A common stock at a price less than the “historical fair market value” (as defined below) will be deemed a share dividend of a number of shares of Class A common stock equal to the product of (i) the number of shares of Class A common stock actually sold in such rights offering (or issuable under any other equity securities sold in such rights offering that are convertible into or exercisable for shares of Class A common stock) and (ii) one minus the quotient of (x) the price per share of Class A common

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stock paid in such rights offering and (y) the historical fair market value. For these purposes, (i) if the rights offering is for securities convertible into or exercisable for shares of Class A common stock, in determining the price payable for Class A common stock, there will be taken into account any consideration received for such rights, as well as any additional amount payable upon exercise or conversion and (ii) “historical fair market value” means the volume weighted average price of Class A common stock as reported during the 10 trading day period ending on the trading day prior to the first date on which the Class A common stock trade on the applicable exchange or in the applicable market, regular way, without the right to receive such rights.

In addition, if we, at any time while the Warrants are outstanding and unexpired, pay a dividend or make a distribution in cash, securities or other assets to all or substantially all of the holders of the Class A common stock on account of such Class A common stock (or other securities into which the Warrants are convertible), other than (a) as described above, (b) any cash dividends or cash distributions which, when combined on a per share basis with all other cash dividends and cash distributions paid on the Class A common stock during the 365-day period ending on the date of declaration of such dividend or distribution does not exceed $0.50 (as adjusted to appropriately reflect any other adjustments and excluding cash dividends or cash distributions that resulted in an adjustment to the exercise price or to the number of shares of Class A common stock issuable on exercise of each Warrant) but only with respect to the amount of the aggregate cash dividends or cash distributions equal to or less than $0.50 per share, or (c) to satisfy the redemption rights of the holders of Class A common stock in connection with a shareholder vote to amend our Charter with respect to any provision relating to the rights of holders of our Class A common stock, then the Warrant exercise price will be decreased, effective immediately after the effective date of such event, by the amount of cash and/or the fair market value of any securities or other assets paid on each share of Class A common stock in respect of such event.

If the number of outstanding shares of Class A common stock is decreased by a consolidation, combination, reverse share sub-division or reclassification of Class A common stock or other similar event, then, on the effective date of such consolidation, combination, reverse share subdivision, reclassification or similar event, the number of shares of Class A common stock issuable on exercise of each Warrant will be decreased in proportion to such decrease in outstanding shares of Class A common stock.

Whenever the number of shares of Class A common stock purchasable upon the exercise of the Warrants is adjusted, as described above, the Warrant exercise price will be adjusted by multiplying the Warrant exercise price immediately prior to such adjustment by a fraction (x) the numerator of which will be the number of shares of Class A common stock purchasable upon the exercise of the Warrants immediately prior to such adjustment and (y) the denominator of which will be the number of shares of Class A common stock so purchasable immediately thereafter.

In case of any reclassification or reorganization of the outstanding Class A common stock (other than those described above or that solely affects the par value of such Class A common stock), or in the case of any merger or consolidation of us with or into another corporation (other than a consolidation or merger in which we are the continuing corporation and that does not result in any reclassification or reorganization of our outstanding Class A common stock), or in the case of any sale or conveyance to another corporation or entity of the assets or other property of us as an entirety or substantially as an entirety in connection with which we are dissolved, the holders of the Warrants will thereafter have the right to purchase and receive, upon the basis and upon the terms and conditions specified in the Warrants and in lieu of the Class A common stock immediately theretofore purchasable and receivable upon the exercise of the rights represented thereby, the kind and amount of Class A common stock or other securities or property (including cash) receivable upon such reclassification, reorganization, merger or consolidation, or upon a dissolution following any such sale or transfer, that the holder of the Warrants would have received if such holder had exercised their Warrants immediately prior to such event. However, if such holders were entitled to exercise a right of election as to the kind or amount of securities, cash or other assets receivable upon such consolidation or merger, then the kind and amount of securities, cash or other assets for which each Warrant will become exercisable will be deemed to be the weighted average of the kind and amount received per share by such holders in such consolidation or merger that affirmatively make such

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election, and if a tender, exchange or redemption offer has been made to and accepted by such holders (other than a tender, exchange or redemption offer made by the Company in connection with redemption rights held by shareholders of the Company as provided for in our Charter) under circumstances in which, upon completion of such tender or exchange offer, the maker thereof, together with members of any group (within the meaning of Rule 13d-5(b)(1) under the Exchange Act) of which such maker is a part, and together with any affiliate or associate of such maker (within the meaning of Rule 12b-2 under the Exchange Act) and any members of any such group of which any such affiliate or associate is a part, own beneficially (within the meaning of Rule 13d-3 under the Exchange Act) more than 50% of the issued and outstanding Class A common stock, the holder of a Warrant will be entitled to receive the highest amount of cash, securities or other property to which such holder would actually have been entitled as a shareholder if such Warrant holder had exercised the Warrant prior to the expiration of such tender or exchange offer, accepted such offer and all of the Class A common stock held by such holder had been purchased pursuant to such tender or exchange offer, subject to adjustment (from and after the consummation of such tender or exchange offer) as nearly equivalent as possible to the adjustments provided for in the Warrant Agreement. If less than 70% of the consideration receivable by the holders of Class A common stock in such a transaction is payable in the form of Class A common stock in the successor entity that is listed for trading on a national securities exchange or is quoted in an established over-the-counter market, or is to be so listed for trading or quoted immediately following such event, and if the registered holder of the Warrant properly exercises the Warrant within thirty days following public disclosure of such transaction, the Warrant exercise price will be reduced as specified in the Warrant Agreement based on the Black-Scholes value (as defined in the Warrant Agreement) of the Warrant. The purpose of such exercise price reduction is to provide additional value to holders of the Warrants when an extraordinary transaction occurs during the exercise period of the Warrants pursuant to which the holders of the Warrants otherwise do not receive the full potential value of the Warrants.

The Warrants were issued in registered form under a Warrant Agreement between Continental Stock Transfer & Trust Company, as Warrant Agent, and us. The Warrant Agreement provides that the terms of the Warrants may be amended without the consent of any holder for the purpose of (i) curing any ambiguity or correcting any mistake, including to conform the provisions of the Warrant Agreement to the description of the terms of the Warrants and the Warrant Agreement set forth in the Altimar II IPO prospectus, or defective provision, (ii) amending the provisions relating to cash dividends on shares as contemplated by and in accordance with the Warrant Agreement or (iii) adding or changing any provisions with respect to matters or questions arising under the Warrant Agreement as the parties to the Warrant Agreement may deem necessary or desirable and that the parties deem to not adversely affect the rights of the registered holders of the Warrants, provided that the approval by the holders of at least 50% of the then-outstanding Public Warrants is required to make any change that adversely affects the interests of the registered holders. A copy of the Warrant Agreement, which was filed as an exhibit to our Annual Report on Form 10-K for the fiscal year ended December 31, 2021, contains a complete description of the terms and conditions applicable to the Warrants.

The Warrant holders do not have the rights or privileges of holders of shares and any voting rights until they exercise their Warrants and receive Class A common stock. After the issuance of Class A common stock upon exercise of the Warrants, each holder will be entitled to one vote for each share held of record on all matters to be voted on by shareholders.

No fractional Warrants were issuable upon separation of the Altimar II units and only whole Warrants will trade. If, upon exercise of the Warrants, a holder would be entitled to receive a fractional interest in a share, we will, upon exercise, round down to the nearest whole number the number of shares of Class A common stock to be issued to the Warrant holder.

We have agreed that, subject to applicable law, any action, proceeding or claim against us arising out of or relating in any way to the Warrant Agreement will be brought and enforced in the courts of the State of New York or the United States District Court for the Southern District of New York, and we irrevocably submit to such jurisdiction, which jurisdiction will be the exclusive forum for any such action, proceeding or claim. This

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provision applies to claims under the Securities Act but does not apply to claims under the Exchange Act or any claim for which the federal district courts of the United States of America are the sole and exclusive forum.

Private Placement Warrants. Except as described below, the Private Placement Warrants have terms and provisions that are identical to those of the Warrants sold as part of the units in the Altimar II IPO. The Private Placement Warrants (including the Class A common stock issuable upon exercise of the Private Placement Warrants) were not transferable, assignable or salable until 30 days after the completion of the Business Combination (except pursuant to limited exceptions to our officers and directors and other persons or entities affiliated with the initial purchasers of the Private Placement Warrants) and they will not be redeemable by us so long as they are held by the Sponsor or its permitted transferees. Sponsor, or its permitted transferees, has the option to exercise the Private Placement Warrants on a cashless basis. If the Private Placement Warrants are held by holders other than the Sponsor or its permitted transferees, the Private Placement Warrants will be redeemable by us in all redemption scenarios and exercisable by the holders on the same basis as the Warrants included in the units being sold in the Altimar II IPO. Any amendment to the terms of the Private Placement Warrants or any provision of the Warrant Agreement with respect to the Private Placement Warrants will require a vote of holders of at least 50% of the number of the then outstanding Private Placement Warrants.

If holders of the Private Placement Warrants elect to exercise them on a cashless basis, they would pay the exercise price by surrendering his, her or its Warrants for that number of Class A common stock equal to the quotient obtained by dividing (x) the product of the number of Class A common stock underlying the Warrants, multiplied by the excess of the “Sponsor fair market value” (defined below) over the exercise price of the Warrants by (y) the Sponsor fair market value. For these purposes, the “Sponsor fair market value” means the average reported closing price of the Class A common stock for the 10 trading days ending on the third trading day prior to the date on which the notice of Warrant exercise is sent to the Warrant Agent.

Transfer Agent, Warrant Agent and Registrar.

The transfer agent and registrar for the Fathom’s Class A common stock and the Warrant Agent for the Warrants is Continental Stock Transfer & Trust Company.

Listing.

Our Class A Shares and our Warrants to purchase Class A Shares are listed on The New York Stock Exchange under the symbols “FATH” and “FATH.WS,” respectively.

SELLING SECURITYHOLDERS

This prospectus relates to the resale by the applicable Selling Securityholders from time to time of up to 152,893,484 shares of Class A common stock and up to 9,900,000 Private Placement Warrants. The Selling Securityholders may from time to time offer and sell any or all of the Class A common stock or Private Placement Warrants, as applicable, set forth below pursuant to this prospectus and any accompanying prospectus supplement. When we refer to the “Selling Securityholders” in this prospectus, we mean the entities and persons listed in the table below, and the pledgees, donees, transferees, assignees, successors, designees and others who later come to hold any of the Selling Securityholders’ interest in the Class A common stock and Private Placement Warrants, as applicable, other than through a public sale.

The following table sets forth, as of January 14, 2022, the names of the Selling Securityholders and the number of shares of Class A common stock and Private Placement Warrants, as applicable, they wished to be covered by this registration statement and eligible for sale under this prospectus. Since the filing of the original registration statements to which this prospectus relates, any Selling Securityholder may have sold or transferred some or all of the securities listed below with respect to such Selling Securityholder, and may in the future sell or

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transfer some or all of the securities listed below in transactions exempt from the registration requirements of the Securities Act rather than pursuant to this prospectus. We cannot advise you as to whether any of the Selling Securityholders will in fact sell any or all of such shares of Class A common stock and Private Placement Warrants, as applicable.

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CERTAIN U.S. FEDERAL INCOME TAX CONSIDERATIONS

The following is a discussion of certain material U.S. federal income tax consequences of the acquisition, ownership and disposition of our Class A common stock and Warrants, which we refer to collectively as our securities. This discussion is limited to certain U.S. federal income tax considerations to beneficial owners of our securities who are initial purchasers of our securities pursuant to this offering and hold our securities as a capital asset within the meaning of Section 1221 of the U.S. Internal Revenue Code of 1986, as amended (the “Code”). This discussion assumes that any distributions made by us on our securities and any consideration received by a holder in consideration for the sale or other disposition of our securities will be in U.S. dollars.

This summary is based upon U.S. federal income tax laws as of the date of this prospectus, which is subject to change or differing interpretations, possibly with retroactive effect. This discussion is a summary only and

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does not describe all of the tax consequences that may be relevant to you in light of your particular circumstances, including but not limited to the alternative minimum tax, the Medicare tax on certain net investment income and the different consequences that may apply if you are subject to special rules that apply to certain types of investors, including but not limited to:

If a partnership (including an entity or arrangement treated as a partnership or other pass-thru entity for U.S. federal income tax purposes) holds our securities, the tax treatment of a partner, member or other beneficial owner in such partnership will generally depend upon the status of the partner, member or other beneficial owner, the activities of the partnership and certain determinations made at the partner, member or other beneficial owner level. If you are a partner, member or other beneficial owner of a partnership holding our securities, you are urged to consult your tax advisor regarding the tax consequences of the acquisition, ownership and disposition of our securities.

This discussion is based on the Code, and administrative pronouncements, judicial decisions and final, temporary and proposed Treasury regulations as of the date hereof, which are subject to change, possibly on a retroactive basis, and changes to any of which subsequent to the date of this prospectus may affect the tax consequences described herein. This discussion does not address any aspect of state, local or non-U.S. taxation, or any U.S. federal taxes other than income taxes (such as gift and estate taxes).

We have not sought, and do not expect to seek, a ruling from the U.S. Internal Revenue Service (the “IRS”) as to any U.S. federal income tax consequence described herein. The IRS may disagree with the discussion herein, and its determination may be upheld by a court. Moreover, there can be no assurance that future legislation, regulations, administrative rulings or court decisions will not adversely affect the accuracy of the statements in this discussion. You are urged to consult your tax advisor with respect to the application of U.S. federal tax laws to your particular situation, as well as any tax consequences arising under the laws of any state, local or foreign jurisdiction.

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THIS DISCUSSION IS ONLY A SUMMARY OF CERTAIN U.S. FEDERAL INCOME TAX CONSIDERATIONS ASSOCIATED WITH THE ACQUISITION, OWNERSHIP AND DISPOSITION OF OUR SECURITIES. EACH PROSPECTIVE INVESTOR IN OUR SECURITIES IS URGED TO CONSULT ITS OWN TAX ADVISOR WITH RESPECT TO THE PARTICULAR TAX CONSEQUENCES TO SUCH INVESTOR OF THE ACQUISITION, OWNERSHIP AND DISPOSITION OF OUR SECURITIES, INCLUDING THE APPLICABILITY AND EFFECT OF ANY U.S. FEDERAL NON-INCOME, STATE, LOCAL, AND NON-U.S. TAX LAWS.

U.S. Holders

This section applies to you if you are a “U.S. Holder.” A U.S. Holder is a beneficial owner of our securities who or that is, for U.S. federal income tax purposes:

Taxation of Distributions. If we pay distributions or make constructive distributions (other than certain distributions of our stock or rights to acquire our stock) to U.S. Holders of our Class A common stock, such distributions generally will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Distributions in excess of current and accumulated earnings and profits will constitute a return of capital that will be applied against and reduce (but not below zero) the U.S. Holder’s adjusted tax basis in its Class A common stock. Any remaining excess will be treated as gain realized on the sale or other disposition of Class A common stock and will be treated as described under “U.S. Holders—Gain or Loss on Sale, Taxable Exchange or Other Taxable Disposition of Class A common stock” below.

Dividends we pay to a U.S. Holder that is a taxable corporation generally will qualify for the dividends received deduction if the requisite holding period is satisfied. With certain exceptions (including, but not limited to, dividends treated as investment income for purposes of investment interest deduction limitations), and provided certain holding period requirements are met, dividends we pay to a non-corporate U.S. Holder may constitute “qualified dividends” that will be subject to tax at the maximum tax rate accorded to long-term capital gains. If the holding period requirements are not satisfied, a corporation may not be able to qualify for the dividends received deduction and would have taxable income equal to the entire dividend amount, and non-corporate U.S. Holders may be subject to tax on such dividend at regular ordinary income tax rates instead of the preferential rate that applies to qualified dividend income.

Gain or Loss on Sale, Taxable Exchange or Other Taxable Disposition of Class A common stock. Upon a sale or other taxable disposition of our Class A common stock, a U.S. Holder generally will recognize capital gain or loss in an amount equal to the difference between the amount realized and the U.S. Holder’s adjusted tax basis in its Class A common stock. Any such capital gain or loss generally will be long-term capital gain or loss if the U.S. Holder’s holding period for the Class A common stock so disposed of exceeds one year. Long-term capital gains recognized by non- corporate U.S. Holders may be eligible to be taxed at reduced rates. The deductibility of capital losses is subject to limitations.

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Generally, the amount of gain or loss recognized by a U.S. Holder is an amount equal to the difference between (i) the sum of the amount of cash and the fair market value of any property received in such disposition and (ii) the U.S. Holder’s adjusted tax basis in its Class A common stock so disposed of. A U.S. Holder’s adjusted tax basis in its Class A common stock generally will equal the U.S. Holder’s acquisition cost (or, in the case of Class A common stock received upon exercise of a warrant, the U.S. Holder’s initial basis for such Class A common stock, as discussed below), less any prior distributions treated as a return of capital.

Exercise of a Warrant. Except as discussed below with respect to the cashless exercise of a warrant, a U.S. Holder generally will not recognize taxable gain or loss upon the exercise of a Warrant for cash. The U.S. Holder’s initial tax basis in the share of our Class A common stock received upon exercise of the Warrant will generally be an amount equal to the sum of the U.S. Holder’s acquisition cost of the Warrant and the exercise price of such warrant. It is unclear whether a U.S. Holder’s holding period for the Class A common stock received upon exercise of the Warrant would commence on the date of exercise of the Warrant or the day following the date of exercise of the Warrant; however, in either case the holding period will not include the period during which the U.S. Holder held the Warrants.

The tax consequences of a cashless exercise of a Warrant are not clear under current tax law. A cashless exercise may be nontaxable, either because the exercise is not a realization event or because the exercise is treated as a recapitalization for U.S. federal income tax purposes. In either situation, a U.S. Holder’s initial tax basis in the Class A common stock received generally should equal the holder’s adjusted tax basis in the warrant. If the cashless exercise were treated as not being a realization event, it is unclear whether a U.S. Holder’s holding period for the Class A common stock would commence on the date of exercise of the Warrant or the day following the date of exercise of the Warrant; in either case, the holding period would not include the period during which the U.S. Holder held the warrant. If, instead, the cashless exercise were treated as a recapitalization, the holding period of the Class A common stock generally would include the holding period of the warrant.

It is also possible that a cashless exercise of a Warrant could be treated in part as a taxable exchange in which gain or loss is recognized. In such event, a U.S. Holder could be deemed to have surrendered a portion of the Warrants being exercised having a value equal to the exercise price of such Warrants in satisfaction of such exercise price. Although not free from doubt, such U.S. Holder generally should recognize capital gain or loss in an amount equal to the difference between the fair market value of the Warrants deemed surrendered to satisfy the exercise price and the U.S. Holder’s adjusted tax basis in such Warrants. In this case, a U.S. Holder’s initial tax basis in the Class A common stock received would equal the sum of the exercise price and the U.S. Holder’s adjusted tax basis in the Warrants exercised. It is unclear whether a U.S. Holder’s holding period for the Class A common stock would commence on the date of exercise of the Warrant or the day following the date of exercise of the Warrant; in either case, the holding period would not include the period during which the U.S. Holder held the Warrant.

Due to the uncertainty and absence of authority on the U.S. federal income tax treatment of a cashless exercise, including when a U.S. Holder’s holding period would commence with respect to the Class A common stock received, there can be no assurance which, if any, of the alternative tax consequences and holding periods described above would be adopted by the IRS or a court of law. Accordingly, U.S. Holders are urged to consult their tax advisors regarding the tax consequences of a cashless exercise.

Sale, Exchange, Redemption or Expiration of a Warrant. Upon a sale, exchange (other than by exercise), redemption (other than a redemption for Class A common stock), or expiration of a warrant, a U.S. Holder will recognize taxable gain or loss in an amount equal to the difference between (1) the amount realized upon such disposition or expiration and (2) the U.S. Holder’s adjusted tax basis in the warrant. A U.S. Holder’s adjusted tax basis in its Warrants will generally equal the U.S. Holder’s acquisition cost, increased by the amount of any constructive distributions included in income by such U.S. Holder (as described below under “U.S. Holders—Possible Constructive Distributions”). Such gain or loss generally will be treated as long-term capital gain or loss if the Warrant is held by the U.S. Holder for more than one year at the time of such disposition or expiration. If a

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Warrant is allowed to lapse unexercised, a U.S. Holder will generally recognize a capital loss equal to such holder’s adjusted tax basis in the warrant. The deductibility of capital losses is subject to certain limitations.

A redemption of Warrants for Class A common stock described in this prospectus under “Description of Securities—Warrants—Public Warrants” should be treated as a “recapitalization” for U.S. federal income tax purposes. Accordingly, you should not recognize any gain or loss on the redemption of Warrants for shares of our Class A common stock. Your aggregate initial tax basis in the shares of Class A common stock received in the redemption should equal your aggregate adjusted tax basis in your Warrants redeemed and your holding period for the shares of Class A common stock received in redemption of your Warrants should include your holding period for your surrendered Warrants.

Possible Constructive Distributions. The terms of each Warrant provide for an adjustment to the number of shares of Class A common stock for which the Warrant may be exercised or to the exercise price of the Warrant in certain events, as discussed in the section of this prospectus captioned “Description of Our Securities—Warrants—Public Warrants.” An adjustment which has the effect of preventing dilution generally should not be a taxable event. Nevertheless, a U.S. Holder of Warrants would be treated as receiving a constructive distribution from us if, for example, the adjustment increases the holder’s proportionate interest in our assets or earnings and profits (e.g., through an increase in the number of shares of Class A common stock that would be obtained upon exercise) as a result of a distribution of cash to the holders of shares of our Class A common stock which is taxable to such holders as a distribution. Such constructive distribution would be subject to tax as described above under “U.S. Holders—Taxation of Distributions” in the same manner as if such U.S. Holder received a cash distribution from us on Class A common stock equal to the fair market value of such increased interest. For certain information reporting purposes, we are required to determine the date and amount of any such constructive distributions. Recently proposed Treasury regulations, which we may rely on prior to the issuance of final regulations, specify how the date and amount of constructive distributions are determined.

Information Reporting and Backup Withholding. In general, information reporting requirements may apply to dividends paid to a U.S. Holder and to the proceeds of the sale or other disposition of our securities, unless the U.S. Holder is an exempt recipient. Backup withholding may apply to such payments if the U.S. Holder fails to provide a taxpayer identification number, a certification of exempt status or has been notified by the IRS that it is subject to backup withholding (and such notification has not been withdrawn).

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules will be allowed as a credit against a U.S. Holder’s U.S. federal income tax liability and may entitle such holder to a refund, provided the required information is timely furnished to the IRS.

Non-U.S. Holders

This section applies to you if you are a “Non-U.S. Holder.” As used herein, the term “Non-U.S. Holder” means a beneficial owner of our securities who or that is for U.S. federal income tax purposes:

but generally does not include an individual who is present in the United States for 183 days or more in the taxable year of the disposition. If you are such an individual, you should consult your tax advisor regarding the U.S. federal income tax consequences of the acquisition, ownership or sale or other disposition of our securities.

Taxation of Distributions. In general, any distributions we make to a Non-U.S. Holder of shares of our Class A common stock, to the extent paid out of our current or accumulated earnings and profits (as determined

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under U.S. federal income tax principles), will constitute dividends for U.S. federal income tax purposes and, provided such dividends are not effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States, we will be required to withhold tax from the gross amount of the dividend at a rate of 30%, unless such Non-U.S. Holder is eligible for a reduced rate of withholding tax under an applicable income tax treaty and provides proper certification of its eligibility for such reduced rate (usually on an IRS Form W-8BEN or W-8BEN-E). Any distribution not constituting a dividend will be treated first as reducing (but not below zero) the Non-U.S. Holder’s adjusted tax basis in its shares of our Class A common stock and, to the extent such distribution exceeds the Non-U.S. Holder’s adjusted tax basis, as gain realized from the sale or other disposition of our securities, which will be treated as described under “Non-U.S. Holders—Gain on Sale, Taxable Exchange or Other Taxable Disposition of Class A common stock and Warrants” below. In addition, if we determine that we are likely to be classified as a “United States real property holding corporation” (see “Non-U.S. Holders—Gain on Sale, Taxable Exchange or Other Taxable Disposition of Class A common stock and Warrants” below), we generally will withhold 15% of any distribution that exceeds our current and accumulated earnings and profits.

The withholding tax generally does not apply to dividends paid to a Non-U.S. Holder who provides a Form W-8ECI, certifying that the dividends are effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States. Instead, the effectively connected dividends will be subject to regular U.S. federal income tax as if the Non-U.S. Holder were a U.S. resident, subject to an applicable income tax treaty providing otherwise. A corporate Non-U.S. Holder receiving effectively connected dividends may also be subject to an additional “branch profits tax” imposed at a rate of 30% (or a lower applicable treaty rate).

Gain on Sale, Taxable Exchange or Other Taxable Disposition of Class A common stock and Warrants. A Non-U.S. Holder generally will not be subject to U.S. federal income or withholding tax in respect of gain recognized on a sale, taxable exchange or other taxable disposition of our securities shares unless:

Unless an applicable treaty provides otherwise, gain described in the first bullet point above will be subject to tax at generally applicable U.S. federal income tax rates as if the Non-U.S. Holder were a U.S. resident. Any gains described in the first bullet point above of a Non-U.S. Holder that is treated as a foreign corporation for U.S. federal income tax purposes may also be subject to an additional “branch profits tax” imposed at a 30% rate (or lower treaty rate).

If the second bullet point above applies to a Non-U.S. Holder, gain recognized by such Holder on the sale, exchange or other disposition of our Class A common stock or Warrants will be subject to tax at generally applicable U.S. federal income tax rates. In addition, a buyer of our Class A common stock or Warrants from such Selling Stockholder may be required to withhold U.S. federal income tax at a rate of 15% of the amount realized upon such disposition. We will be classified as a United States real property holding corporation if the fair market value of our “United States real property interests” equals or exceeds 50% of the sum of the fair market value of our worldwide real property interests plus our other assets used or held for use in a trade or business, as determined for U.S. federal income tax purposes. We do not expect to be a United States real property holding corporation immediately after the business combination is completed.

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Possible Constructive Distributions. The terms of each Warrant provide for an adjustment to the number of shares of Class A common stock for which the Warrant may be exercised or to the exercise price of the Warrant in certain events, as discussed in the section of this prospectus captioned “Description of Our Securities—Warrants—Public Warrants.” An adjustment which has the effect of preventing dilution generally should not be a taxable event. Nevertheless, a Non-U.S. Holder of Warrants would be treated as receiving a constructive distribution from us if, for example, the adjustment increases the holder’s proportionate interest in our assets or earnings and profits (e.g., through an increase in the number of shares of Class A common stock that would be obtained upon exercise) as a result of a distribution of cash to the holders of shares of our Class A common stock which is taxable to such holders as a distribution. A Non-U.S. Holder would be subject to U.S. federal income tax withholding as described above under “Non-U.S. Holders—Taxation of Distributions” under that section in the same manner as if such non-U.S. Holder received a cash distribution from us on Class A common stock equal to the fair market value of such increased interest.

Information Reporting and Backup Withholding. Information returns will be filed with the IRS in connection with payments of dividends and the proceeds from a sale or other disposition of our Class A common stock and Warrants. A Non-U.S. Holder may have to comply with certification procedures to establish that it is not a United States person in order to avoid information reporting and backup withholding requirements. The certification procedures required to claim a reduced rate of withholding under a treaty generally will satisfy the certification requirements necessary to avoid the backup withholding as well. Backup withholding is not an additional tax. The amount of any backup withholding from a payment to a Non-U.S. Holder will be allowed as a credit against such holder’s U.S. federal income tax liability and may entitle such holder to a refund, provided that the required information is timely furnished to the IRS.

FATCA Withholding Taxes. Provisions commonly referred to as “FATCA” generally impose withholding at a rate of 30% on payments of dividends (including constructive dividends) in respect to our securities which are held by or through certain foreign financial institutions” (which is broadly defined for this purpose and in general includes investment vehicles) and certain other non-U.S. entities unless various U.S. information reporting and due diligence requirements (generally relating to ownership by United States persons of interests in or accounts with those entities) have been satisfied by, or an exemption applies to, the payee (typically certified as to by the delivery of a properly completed IRS Form W-8BEN-E). Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules. Accordingly, the entity through which our Class A common stock are held will affect the determination of whether such withholding is required. Similarly, dividends in respect of our Class A common stock held by an investor that is a non-financial Non-U.S. entity that does not qualify under certain exceptions will generally be subject to withholding at a rate of 30% unless such entity either (1) certifies to us or the applicable withholding agent that such entity does not have any “substantial United States owners” or (2) provide certain information regarding the entity’s “substantial United States owners” which will in turn be provided to the U.S. Department of Treasury. Under certain circumstances, a Non-U.S. Holder might be eligible for refunds or credits of such withholding taxes, and a Non-U.S. Holder might be required to file a U.S. federal income tax return to claim such refunds or credits.

Thirty percent withholding under FATCA was scheduled to apply to payments of gross proceeds from the sale or other disposition of property that produces U.S.-source interest or dividends beginning on January 1, 2019, but on December 13, 2018, the IRS released proposed regulations that, if finalized in their proposed form, would eliminate the obligation to withhold on gross proceeds. Such proposed regulations also delayed withholding on certain other payments received from other foreign financial institutions that are allocable, as provided for under final Treasury Regulations, to payments of U.S.- source dividends, and other fixed or determinable annual or periodic income. Although these proposed Treasury Regulations are not final, taxpayers generally may rely on them until final Treasury Regulations are issued. Prospective investors should consult their tax advisors regarding the effects of FATCA on their investment in our securities.

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Possible Legislative Tax Changes

The foregoing summary of federal income tax law reflects provisions of recent legislation. However, because, Treasury Regulations and other official interpretations have not been issued with respect to a number of such provisions, their meaning is uncertain. In addition, legislation has been or may be proposed in Congress that might have a substantial and adverse effect on U.S. and Non-U.S. Holders. U.S. and Non-U.S. Holders should consult with their own professional advisers as to all current and possible future proposals with respect to federal, state and local tax legislation and the effect, if any, that such legislation may have on an investment in our common stock and Warrants. In addition, the U.S. federal income tax rate (and any other applicable tax rates) may increase during the ownership of the common stock and Warrants and negatively affect the after-tax returns of the U.S. and Non-U.S. Holders. Among other proposed tax changes, the current U.S. presidential administration has proposed increasing the U.S. corporate income tax from its current 21% rate.

PLAN OF DISTRIBUTION

This prospectus relates to the resale of up to 152,893,234 shares of Class A common stock and up to 9,900,00 Private Placement Warrants by the Selling Securityholders from time to time, and the issuance by us of up to 18,525,000 shares of Class A common stock that are issuable upon exercise of the Warrants. The Selling Securityholders will pay any underwriting discounts and commission and expenses incurred by the Selling Securityholders for brokage, accounting, tax or legal services or any other expenses incurred by the Selling Securityholders in disposing of their securities. We are required to pay all fees and expenses incident to the registration of the shares of our Class A common stock to be offered and sold pursuant to this prospectus.

We will not receive any of the proceeds from the sale of these securities by the Selling Securityholders. The aggregate proceeds to the Selling Securityholders will be the purchase price of the securities less any discounts and commissions borne by the Selling Securityholders. We will receive up to an aggregate of $213.0 million from the exercise of the Warrants (and the related issuance by us of shares of Class A common stock underlying the Warrants).

A holder of Warrants may exercise its Warrants in accordance with the Warrant Agreement on or before their expiration date by surrendering, at the office of the Warrant Agent, Continental Stock Transfer & Trust Company, the certificate evidencing such Warrant, an election to purchase, properly completed and duly executed, accompanied by full payment of the exercise price and any and all applicable taxes due in connection with the exercise of the Warrant, subject to any applicable provisions relating to cashless exercises in accordance with the Warrant Agreement.

The Selling Securityholders, which as used herein includes donees, pledgees, transferees, distributees or other successors-in-interest selling shares of our Class A common stock or Private Placement Warrants or interests in our Class A common stock or Private Placement Warrants received after the date of this prospectus from the Selling Securityholders as a gift, pledge, partnership distribution or other transfer, may, from time to time, sell, transfer, distribute or otherwise dispose of certain of their shares of Class A common stock or Private Placement Warrants or interests in our Class A common stock or Private Placement Warrants on any stock exchange, market or trading facility on which shares of our Class A common stock or Private Placement Warrants are traded or in private transactions. These dispositions may be at fixed prices, at prevailing market prices at the time of sale, at prices related to the prevailing market price, at varying prices determined at the time of sale, or at negotiated prices. The Private Placement Warrants are not listed on any stock exchange and we do not intend to list the Private Placement Warrants on any exchange or stock market.

Subject to the limitations set forth in any applicable registration rights agreement, the Selling Securityholders may use any one or more of the following methods when selling the securities offered by this prospectus:

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In addition, a Selling Securityholder that is an entity may elect to make a pro rata in-kind distribution of securities to its members, partners or stockholders pursuant to the registration statement of which this prospectus is a part by delivering a prospectus with a plan of distribution. Such members, partners or stockholders would thereby receive freely tradeable securities pursuant to the distribution through a registration statement. To the extent a distributee is an affiliate of ours (or to the extent otherwise required by law), we may file a prospectus supplement in order to permit the distributees to use the prospectus to resell the securities acquired in the distribution.

There can be no assurance that the Selling Securityholder will sell all or any of the securities offered by this prospectus. In addition, the Selling Securityholders may also sell securities under Rule 144 under the Securities Act, if available, or in other transactions exempt registration, rather than under this prospectus. The Selling Securityholders have the sole and absolute discretion not to accept any purchase offer to make any sale of securities if they deem the purchase price to be unsatisfactory at any particular time.

The Selling Securityholders also may transfer the securities in other circumstances, in which case the transferees, pledgees or other successors-in-interest will be the selling beneficial owners for purposes of this prospectus. Upon being notified by a Selling Securityholder that a donee, pledgee, transferee, other successor-in-interest intends to sell our securities, we will, to the extent required, promptly file a supplement to this prospectus to name specifically such person as a Selling Securityholder.

To the extent required, the shares of our Class A common stock or Private Placement Warrants to be sold, the names of the Selling Securityholders, the respective purchase prices and public offering prices, the names of

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any agents, dealer or underwriter, any applicable commissions or discounts with respect to a particular offer will be set forth in an accompanying prospectus supplement or, if appropriate, a post-effective amendment to the registration statement that includes this prospectus.

In connection with the sale of shares of our Class A common stock or Private Placement Warrants, the Selling Securityholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the shares of our Class A common stock or Private Placement Warrants in the course of hedging the positions they assume. The Selling Securityholders may also sell shares of our Class A common stock or Private Placement Warrants short and deliver these securities to close out their short positions, or loan or pledge the Class A common stock or Private Placement Warrants to broker-dealers that in turn may sell these shares. The Selling Securityholders may also enter into option or other transactions with broker-dealers or other financial institutions or the creation of one or more derivative securities which require the delivery to such broker-dealer or other financial institution of securities offered by this prospectus, which securities such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction). The Selling Securityholders may also pledge securities to a broker-dealer or other financial institution, and, upon a default, such broker-dealer or other financial institution, may effect sales of the pledged securities pursuant to this prospectus (as supplemented or amended to reflect such transactions).

In order to facilitate the offering of the securities, any underwriters or agents, as the case may be, involved in the offering of such securities may engage in transactions that stabilize, maintain or otherwise affect the price of our securities. Specifically, the underwriters or agents, as the case may be, may over all a lot in connection with the offering, creating a short position in our securities for their own account. In addition, to cover overallotments or to stabilize the price of our securities, the underwriters or agents, as the case may be, may bid for, and purchase, such securities in the open market. Finally, in any offering of securities through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allotted to an underwriter or a broker dealer for distributing such securities in the offering if the syndicate repurchases previously distributed securities in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of the securities above independent market levels. The underwriters or agents, as the case may be, are not required to engage in these activities, and may end any of these activities at any time.

The Selling Securityholders may solicit offers to purchase the securities directly from, and it may sell such securities directly to, institutional investors or others. In that case, no underwriters or agents would be involved. The terms of any of those sales, including the terms of any bidding or auction process, if utilized, will be described in the applicable prospectus supplement.

It is possible that one or more underwriters may make a market in our securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot give any assurance as to the liquidity of the trading market for our securities. Fathom’s shares of Class A common stock are currently listed on the NYSE under the symbol “FATH” and its Public Warrants are currently listed on the NYSE under the symbol “FATH.WS.”

The Selling Securityholders may authorize underwriters, broker-dealers or agents to solicit offers by certain purchasers to purchase the securities at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. The contracts will be subject only to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth any commissions we or the Selling Securityholders pay for solicitation of these contracts.

A Selling Securityholder may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those derivatives, the third parties may sell securities covered by this

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prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by any Selling Securityholder or borrowed from any Selling Securityholder or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from any Selling Securityholder in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and will be identified in the applicable prospectus supplement (or a post-effective amendment). In addition, any Selling Securityholder may otherwise loan or pledge securities to a financial institution or other third party that in turn may sell the securities short using this prospectus. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

In effecting sales, broker-dealers or agents engaged by the Selling Securityholders may arrange for other broker-dealers to participate. Broker-dealers or agents may receive commissions, discounts or concessions from the Selling Securityholders in amounts to be negotiated immediately prior to the sale.

In compliance with the guidelines of the Financial Industry Regulatory Authority (“FINRA”), the aggregate maximum discount, commission, fees or other items constituting underwriting compensation to be received by any FINRA member or independent broker-dealer will not exceed 8% of the gross proceeds of any offering pursuant to this prospectus and any applicable prospectus supplement.

If at the time of any offering made under this prospectus a member of FINRA participating in the offering has a “conflict of interest” as defined in FINRA Rule 5121 (“Rule 5121”), that offering will be conducted in accordance with the relevant provisions of Rule 5121.

To our knowledge, there are currently no plans, arrangements or understandings between the Selling Securityholders and any broker-dealer or agent regarding the sale of the securities by the Selling Securityholders. Upon our notification by a Selling Securityholder that any material arrangement has been entered into with an underwriter or broker-dealer for the sale of securities through a block trade, special offering, exchange distribution, secondary distribution or a purchase by an underwriter or broker-dealer, we will file, if required by applicable law or regulation, a supplement to this prospectus pursuant to Rule 424(b) under the Securities Act disclosing certain material information relating to such underwriter or broker-dealer and such offering.

Underwriters, broker-dealers or agents may facilitate the marketing of an offering online directly or through one of their affiliates. In those cases, prospective investors may view offering terms and a prospectus online and, depending upon the particular underwriter, broker-dealer or agent, place orders online or through their financial advisors.

In offering the securities covered by this prospectus, the Selling Securityholders and any underwriters, broker- dealers or agents who execute sales for the Selling Securityholders may be deemed to be “underwriters” within the meaning of the Securities Act in connection with such sales. Any discounts, commissions, concessions or profit they earn on any resale of those securities may be underwriting discounts and commissions under the Securities Act.

The underwriters, broker-dealers and agents may engage in transactions with us or the Selling Securityholders, or perform services for us or the Selling Securityholders, in the ordinary course of business.

In order to comply with the securities laws of certain states, if applicable, the securities must be sold in such jurisdictions only through registered or licensed brokers or dealers. In addition, in certain states the securities may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from the registration or qualification requirement is available and is complied with.

The Selling Securityholders and any other persons participating in the sale or distribution of the securities will be subject to applicable provisions of the Securities Act and the Exchange Act, and the rules and regulations

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thereunder, including, without limitation, Regulation M. These provisions may restrict certain activities of, and limit the timing of purchases and sales of any of the securities by, the Selling Securityholders or any other person, which limitations may affect the marketability of the shares of the securities.

We will make copies of this prospectus (as it may be supplemented or amended from time to time) available to the Selling Securityholders for the purpose of satisfying the prospectus delivery requirements of the Securities Act. The Selling Securityholders may indemnify any agent, broker-dealer or underwriter that participates in transactions involving the sale of the securities against certain liabilities, including liabilities arising under the Securities Act.

We have agreed to indemnify the Selling Securityholders against certain liabilities, including certain liabilities under the Securities Act, the Exchange Act or other federal or state law. Agents, broker-dealers and underwriters may be entitled to indemnification by us and the Selling Securityholders against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments which the agents, broker-dealers or underwriters may be required to make in respect thereof.

LEGAL MATTERS

Winston & Strawn LLP has passed upon the validity of the securities offered by this prospectus and certain other legal matters related to this prospectus.

EXPERTS

The audited consolidated financial statements incorporated by reference in this prospectus and elsewhere in the registration statement have been so incorporated by reference in reliance upon the report of Grant Thornton LLP (“GT”), independent registered public accountants, upon the authority of said firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3, including exhibits, under the Securities Act, with respect to the securities offered by this prospectus. This prospectus, which forms a part of such registration statement, does not contain all of the information included in the registration statement. For further information pertaining to us and our securities, you should refer to the registration statement and to its exhibits. The registration statement has been filed electronically and may be obtained in any manner listed below. Whenever we make reference in this prospectus to any of our contracts, agreements or other documents, the references are not necessarily complete. If a contract or document has been filed as an exhibit to the registration statement or a report we file under the Exchange Act that is incorporated by reference into the registration statement, you should refer to the copy of the contract or document that has been filed. Each statement in this prospectus relating to a contract or document filed as an exhibit to a registration statement or report is qualified in all respects by the filed exhibit.

In addition, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public on a website maintained by the SEC located at www.sec.gov. We also maintain a website at www.fathommfg.com. Through our website, we make available, free of charge, annual, quarterly and current reports, proxy statements and other information as soon as reasonably practicable after they are electronically filed with, or furnished to, the SEC. The information contained on, or that may be accessed through, our website is not part of, and is not incorporated into, this prospectus. You may inspect a copy of the registration statement through the SEC’s website, as provided above.

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INFORMATION INCORPORATED BY REFERENCE

The SEC rules allow us to “incorporate by reference” information into this prospectus, which means that we can disclose important information to you by referring you to another document we have filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in any document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in or omitted from this prospectus or any accompanying prospectus supplement, or in any other subsequently filed document which also is or is deemed to be incorporated by reference herein, modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

This prospectus and any accompanying prospectus supplement incorporate by reference the documents set forth below which have previously been filed with the SEC:

We also incorporate by reference into this prospectus any further filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) (other than portions of those made pursuant to Item 2.02 or Item 7.01 of Form 8-K or other information “furnished” and not filed with the SEC), including all filings filed after the date hereof and prior to the completion of an offering of securities under this prospectus.

We have filed with the SEC this registration statement under the Securities Act of 1933, as amended, covering the Class A Shares to be offered and sold by this prospectus and any applicable prospectus supplement. This prospectus does not contain all of the information included in the registration statement, some of which is contained in exhibits to the registration statement. The registration statement, including the exhibits, can be read at the SEC website referred to below under “Where You Can Find More Information.” Any statement made in this prospectus or any prospectus supplement concerning the contents of any contract, agreement or other document is only a summary of the actual contract, agreement or other document. If we have filed any contract, document, agreement or other document as an exhibit to the registration statement or any other document

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incorporated herein by reference, you should read the exhibit for a more complete understanding of the document or matter involved. Each statement regarding a contract, agreement or other document is qualified in its entirety by reference to the actual document.

Our filings with the SEC, including Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports, are available free of charge on our website at www.fathommfg.com as soon as reasonably practicable after they are filed with, or furnished to, the SEC. Our website and the information contained on that site, or connected to that site, are not incorporated into and are not a part of this prospectus. Copies of all documents incorporated by reference in this prospectus, other than exhibits to those documents unless such exhibits are specially incorporated by reference in this prospectus, will be provided at no cost to each person, including any beneficial owner, who receives a copy of this prospectus on the written or oral request of that person made to:

Fathom Digital Manufacturing Corporation

1050 Walnut Ridge Drive

Hartland, WI 53029

Attn: Investor Relations

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FATHOM DIGITAL MANUFACTURING CORPORATION

52,423,250 Shares of Class A Common Stock

9,900,000 Warrants to Purchase Shares of Class A Common Stock

18,525,000 Shares of Class A Common Stock Underlying Warrants to Purchase Class A Common Stock

90,570,234 Shares of Class A Common Stock Underlying Class B Common Stock

PROSPECTUS

May    , 2023

You should rely only on the information contained or incorporated by reference in this prospectus. We have not authorized anyone to provide you with different information. You should not assume that the information contained or incorporated by reference in this prospectus is accurate as of any date other than the date of this prospectus. Neither we nor the Selling Securityholders are making an offer of these securities in any state where the offer is not permitted.

Item 15. Indemnification of Directors and Officers.

Section 145 of the DGCL (“Section 145”) provides that a Delaware corporation may indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of such corporation) by reason of the fact that such person is or was a director, officer, employee or agent of such corporation, or is or was serving at the request of such corporation as a director, officer, employee or agent of another corporation or enterprise. The indemnification may include expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding, provided such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the corporation’s best interests and, with respect to any criminal action or proceeding, had no reasonable cause to believe that his conduct was unlawful. Section 145 also provides that a Delaware corporation may indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of such corporation, under the same conditions, except that such indemnification is limited to expenses (including attorneys’ fees) actually and reasonably incurred by such person, and except that no indemnification is permitted without judicial approval if such person is adjudged to be liable to such corporation. Where an officer or director of a corporation is successful, on the merits or otherwise, in the defense of any action, suit or proceeding referred to above, or any claim, issue or matter therein, the corporation must indemnify that person against the expenses (including attorneys’ fees) which such officer or director actually and reasonably incurred in connection therewith.

Section 145 further authorizes a corporation to purchase and maintain insurance on behalf of any person who is or was a director, officer, employee or agent of the corporation, or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or enterprise, against any liability asserted against such person and incurred by such person in any such capacity, or arising out of such person’s status as such, whether or not the corporation would otherwise have the power to indemnify such person against such liability under Section 145.

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Our certificate of incorporation and bylaws provide that Fathom will indemnify to the fullest extent permitted by law any person made or threatened to be made a party to an action or proceeding, whether criminal, civil, administrative or investigative, by reason of the fact that he, his testator or intestate is or was a director, officer or employee of Fathom or any predecessor of Fathom, or serves or served at any other corporation, partnership, joint venture, trust or other enterprise as a director, officer, employee or agent at the request of Fathom or any predecessor of Fathom.

Our bylaws provide for mandatory indemnification to the fullest extent permitted by DGCL against all expenses (including attorney’s fees), judgments, fines, ERISA excise taxes or penalties and amounts paid in settlements.

Our certificate of incorporation eliminates the liability of a director of Fathom to the fullest extent under applicable law. Pursuant to Section 102(b)(7) of the DGCL, a corporation may eliminate the personal liability of a director to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, except for liabilities arising (i) from any breach of the director’s duty of loyalty to the corporation or its stockholders, (ii) from acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) under Section 174 of the DGCL, or (iv) from any transaction from which the director derived an improper personal benefit.

These provisions may be held not to be enforceable for certain violations of the federal securities laws of the United States.

The Registrant’s directors and executive officers are covered by insurance maintained by Fathom against specified liabilities for actions taken in their capacities as such, including liabilities under the Securities Act. In addition, Fathom has entered into contracts with its directors and executive officers providing indemnification of such directors and executive officers by Fathom to the fullest extent permitted by law, subject to certain limited exceptions.

Item 16. Exhibits.

The following exhibits are included with this filing or incorporated by reference as listed herein:

EXHIBIT INDEX

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Item 17. Undertakings.

The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement: (i) to include any prospectus required by Section 10(a)(3) of the Securities Act of 1933; (ii) to reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement (notwithstanding the foregoing, any increase or decrease in the volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement); and (iii) to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement; provided, however, that paragraphs 1(i), 1(ii) and 1(iii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or 15(d) of the Exchange Act that are incorporated by reference in this registration statement.

(2) That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4) That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser, (i) each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and (ii) each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act of 1933 shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof; provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5) That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser, each prospectus filed pursuant to Rule 424(b) as part of a registration statement relating to an offering, other than

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registration statements relying on Rule 430B or other than prospectuses filed in reliance on Rule 430A, shall be deemed to be part of and included in the registration statement as of the date it is first used after effectiveness. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such first use, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such date of first use.

(6) The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(7) Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers, and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission, such indemnification is against public policy as expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act of 1933 and will be governed by the final adjudication of such issue.

(8) The undersigned registrant hereby undertakes that, (i) for purposes of determining any liability under the Securities Act of 1933, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b) (1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective; and (ii) for the purpose of determining any liability under the Securities Act of 1933, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant has duly caused this Amendment No.1 to Post-Effective Amendment on Form S-3 to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Hartland, WI, on May 22, 2023.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Amendment No.1 to Post-Effective Amendment on Form S-3 has been signed below by the following persons in the capacities indicated below as of May 22, 2023.

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