DIAX Nuveen Dow 30SM Dynamic Overwrite Fund

ITEM 1. REPORTS TO STOCKHOLDERS.

Closed-End Funds

31 December

2020

Nuveen

Closed-End Funds

As permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Funds’ annual and semi-annual shareholder reports will not be sent to you by mail unless you specifically request paper copies of the reports. Instead, the reports will be made available on the Funds’ website (www.nuveen.com), and you will be notified by mail each time a report is posted and provided with a website link to access the report.

You may elect to receive shareholder reports and other communications from the Funds electronically at any time by contacting the financial intermediary (such as a broker-dealer or bank) through which you hold your Fund shares or, if you are a direct investor, by enrolling at www.nuveen.com/e-reports.

You may elect to receive all future shareholder reports in paper free of charge at any time by contacting your financial intermediary or, if you are a direct investor, by calling 800-257-8787 and selecting option #2 or (ii) by logging into your Investor Center account at www.computershare.com/investor and clicking on “Communication Preferences”. Your election to receive reports in paper will apply to all funds held in your account with your financial intermediary or, if you are a direct investor, to all your directly held Nuveen Funds and any other directly held funds within the same group of related investment companies.

Annual Report

IMPORTANT DISTRIBUTION NOTICE

for Shareholders of the Nuveen S&P 500 Buy-Write Income Fund (BXMX), Nuveen Dow 30^SM Dynamic Overwrite Fund (DIAX),

Nuveen S&P 500 Dynamic Overwrite Fund (SPXX) and

Nuveen Nasdaq 100 Dynamic Overwrite Fund (QQQX)

Annual Shareholder Report for the period ending December 31, 2020

The Nuveen S&P 500 Buy-Write Income Fund (BXMX), Nuveen Dow 30SM Dynamic Overwrite Fund (DIAX), Nuveen S&P 500 Dynamic Overwrite Fund (SPXX) and Nuveen Nasdaq 100 Dynamic Overwrite Fund (QQQX) seek to offer attractive cash flow to their shareholders, by converting the expected long-term total return potential of the Funds’ portfolio of investments into regular quarterly distributions. Following is a discussion of the Managed Distribution Policy the Funds use to achieve this.

Each Fund pays quarterly common share distributions that seek to convert the Fund’s expected long-term total return potential into regular cash flow. As a result, the Funds’ regular common share distributions (presently $0.2150, $0.2730, $0.2450 and $0.3900 per share, respectively) may be derived from a variety of sources, including:

Such distributions are sometimes referred to as “managed distributions.” Each Fund seeks to establish a distribution rate that roughly corresponds to the Adviser’s projections of the total return that could reasonably be expected to be generated by each Fund over an extended period of time. The Adviser may consider many factors when making such projections, including, but not limited to, long-term historical returns for the asset classes in which each Fund invests. As portfolio and market conditions change, the distribution amount and distribution rate on the Common Shares under the Funds’ Managed Distribution Policy could change.

When it pays a distribution, each Fund provides holders of its Common Shares a notice of the estimated sources of the Fund’s distributions (i.e., what percentage of the distributions is estimated to constitute ordinary income, short-term capital gains, long-term capital gains, and/or a non-taxable return of capital) on a year-to-date basis. It does this by posting the notice on its website (www.nuveen.com/cef), and by sending it in written form.

You should not draw any conclusions about the Funds’ investment performance from the amount of this distribution or from the terms of the Funds’ Managed Distribution Policy. The Funds’ actual financial performance will likely vary from month-to-month and from year-to-year, and there may be extended periods when the distribution rate will exceed the Funds’ actual total returns. The Managed Distribution Policy provides that the Board may amend or terminate the Policy at any time without prior notice to Fund shareholders. There are presently no reasonably foreseeable circumstances that might cause each Fund to terminate its Managed Distribution Policy.

Table of Contents

3

Chair’s Letter to Shareholders

4

Portfolio Managers’ Comments

Nuveen S&P 500 Buy-Write Income Fund (BXMX)

Nuveen Dow 30^SM Dynamic Overwrite Fund (DIAX)

Nuveen S&P 500 Dynamic Overwrite Fund (SPXX)

Nuveen Nasdaq 100 Dynamic Overwrite Fund (QQQX)

The Nuveen S&P 500 Buy-Write Income Fund (BXMX) features portfolio management by Gateway Investment Advisers, LLC (Gateway). The Fund’s portfolio managers are Kenneth H. Toft, Michael T. Buckius and Daniel M. Ashcraft. Nuveen Dow 30^SM Dynamic Overwrite Fund (DIAX), Nuveen S&P 500 Dynamic Overwrite Fund (SPXX) and Nuveen Nasdaq 100 Dynamic Overwrite Fund (QQQX) feature portfolio management by Nuveen Asset Management, LLC (NAM), an affiliate of Nuveen, Fund Advisors, LLC, the Funds’ investment adviser. The Funds’ portfolio managers are David A. Friar, James Campagna, CFA, Lei Liao, CFA and Darren Tran, CFA.

Investment Policy Changes

During the reporting period, the Board of Trustees of QQQX and SPXX approved a modification to the Funds’ equity portfolio investment strategies. Effective August 3, 2020, DIAX, SPXX and QQQX Fund strategies takes into consideration each Fund’s tax position and employ various techniques, including tax-loss harvesting, to improve after-tax shareholder outcome.

Here the portfolio management team reviews U.S. economic and markets, key investment strategies and the performance of the Funds for the twelve-month reporting period ended December 31, 2020.

What factors affected the U.S. economy and financial markets during the twelve-month reporting period ended December 31, 2020?

The U.S. economy rebounded more quickly than expected from the deep downturn caused by the COVID-19 crisis and containment measures, but it was not fully recovered by the year’s end. U.S. gross domestic product (GDP) grew 4.0% on an annualized basis in the fourth quarter of 2020 and 33.1% (annualized) in the third quarter, but remained down 3.5% in 2020 overall (from the 2019 annual level to the 2020 annual level) as measured by the Bureau of Economic Analysis “advance” estimate. GDP measures the value of goods and services produced by the nation’s economy less the value of the goods and services used up in production, adjusted for price changes. The economy fell into a deep recession in February 2020 due to the restrictions on business and social activity to mitigate the COVID-19 spread. In the first and second quarters of 2020, annualized GDP shrank 5% and 31.4%, respectively. Government relief programs provided significant aid to individuals and businesses as the economy began reopening in May 2020, which helped the economy bounce back strongly over the second half of the year.

This material is not intended to be a recommendation or investment advice, does not constitute a solicitation to buy, sell or hold a security or an investment strategy and is not provided in a fiduciary capacity. The information provided does not take into account the specific objectives or circumstances of any particular investor, or suggest any specific course of action. Investment decisions should be made based on an investor’s objectives and circumstances and in consultation with his or her advisors.

Certain statements in this report are forward-looking statements. Discussions of specific investments are for illustration only and are not intended as recommendations of individual investments. The forward-looking statements and other views expressed herein are those of the portfolio managers as of the date of this report. Actual future results or occurrences may differ significantly from those anticipated in any forward-looking statements and the views expressed herein are subject to change at any time, due to numerous market and other factors. The Funds disclaim any obligation to update publicly or revise any forward-looking statements or views expressed herein.

Refer to the Glossary of Terms Used in this Report for further definition of the terms used within this section.

5

Portfolio Managers’ Comments (continued)

Consumer spending, the largest driver of the economy, remained resilient despite the disruption caused by the health and economic crisis. Consumer spending declined significantly and unemployment rose sharply starting in March 2020. These measures rebounded markedly in the second half of the year, although the momentum slowed toward year end amid a resurgence of coronavirus infections. The Bureau of Labor Statistics said the unemployment rate rose to 6.7% in December 2020 from 3.6% in December 2019. As of December 2020, slightly more than half of the 22 million jobs lost in March and April 2020 have been recovered. The average hourly earnings rate appeared to increase, growing at an annualized rate of 5.1% in December 2020, despite the spike in unemployment. Earnings data was skewed by the concentration of job losses in lower-wage work, which effectively eliminated most of the low-wage data, resulting in an average of mostly higher numbers. The overall trend of inflation remained muted, as decreases in gasoline, apparel and transportation prices offset an increase in food prices. The Bureau of Labor Statistics said the Consumer Price Index (CPI) increased 1.4% over the twelve-month reporting period ended December 31, 2020 before seasonal adjustment.

Prior to the COVID-19 crisis recession, the U.S. Federal Reserve (the Fed) had reduced its benchmark interest rate to support the economy’s slowing growth. The Fed also stopped shrinking its bond portfolio sooner than scheduled and began buying short-term Treasury bills to help money markets operate smoothly and maintain short-term borrowing rates at low levels. As the health and economic crisis deepened, the Fed enacted an array of emergency measures in March 2020 to stabilize the financial system and support the markets, including cutting its main interest rate to near zero, offering lending programs to aid small and large companies and allowing unlimited bond purchases, known as quantitative easing. In August 2020, the Fed announced a change in inflation policy to average inflation targeting. Under this regime, the Fed will tolerate the inflation rate temporarily overshooting the target rate to offset periods of below-target inflation, so that inflation averages a 2% rate over time. Fed officials remained cautious, acknowledging the economy’s improvement but concerned about near-term weakness, and left policy unchanged over the remainder of their meetings in 2020.

In March and April 2020, the U.S. government approved three aid packages. These included $2 trillion allocated across direct payments to Americans, an expansion of unemployment insurance, loans to large and small businesses, funding to hospitals and health agencies and support to state and local governments, and more than $100 billion in funding to health agencies and employers offering paid leave. In December 2020, the government enacted a $900 billion relief package extending some of these programs. With Joe Biden winning the U.S. presidential election in November 2020, more fiscal stimulus is anticipated in 2021.

The COVID-19 crisis rapidly dwarfed all other market concerns starting in late February 2020. Equity and commodity markets sold off and safe-haven assets rallied in March 2020 as China, other countries and then the United States initiated quarantines, restricted travel and shuttered factories and businesses. The potential economic shock was particularly difficult to assess, which amplified market volatility. An ill-timed oil price war between the Organization of the Petroleum Exporting Countries (OPEC) and non-OPEC member Russia, which caused oil prices to plunge in March 2020, exacerbated the market sell-off. At year end, the announcement of high efficacy rates in several COVID-19 vaccine trials, followed by regulatory authorizations and public vaccination drives across Western countries, improved the outlook for 2021 and led to risk-on sentiment in the markets.

Geopolitical uncertainty remained elevated during 2020 in anticipation of the U.S. presidential election in November 2020 and the Brexit transition period set to expire in December 2020. Political risks eased somewhat toward the end of the reporting period, as markets ultimately viewed a Biden administration positively and the European Union (EU) and United Kingdom (U.K.) finalized a trade deal in the final days of the transition period. Although China and the U.S. signed a “phase one” trade deal in January 2020, tensions continued to flare over other trade and technology/security issues, Hong Kong’s sovereignty and the management of the COVID-19 crisis.

The turmoil caused by the COVID-19 crisis drove a significant shift in measures of realized volatility, implied volatility and the dynamic relationship between the two. Volatility measures at the beginning of the reporting period were

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consistent with the below average readings persistent in recent years. The reporting period began with the Cboe^® Volatility Index^® (the VIX^®) reaching its low of 12.10 on January 17, 2020 and did not break above its long-term average of 19.47 until February 24, 2020, the first time the S&P 500^® Index had a loss exceeding 3% during 2020. The VIX^® rose as high as 85.47 on March 18, 2020, just shy of its all-time intra-day high reading of 89.53 set in 2008. Realized volatility measures in 2020 were even more extreme. The S&P 500^® Index would record 16 more one-day losses exceeding 3%, eight of which occurred in March 2020 alone. The large swings resulted in a 93.44% annualized standard deviation of daily returns for the S&P 500^® Index in March 2020, the highest reading of monthly standard deviation in history, dating back to 1928. The massive spike in realized volatility caused the typical relationship between implied and realized volatility to invert. Typically, implied volatility measures exceed realized volatility, and this relationship has held about 90% of the time on a monthly basis since 1990. The March 2020 inversion was the largest on record, nearly 50% larger than the previous record established in September 2008. While it was extreme, the inversion was temporary as realized volatility normalized more quickly than implied volatility. After implied volatility peaked in mid-March 2020, the VIX^® trended lower while the spread between implied and realized volatility flipped back to positive in April 2020 and remained positive each subsequent month of the reporting period. Moreover, the August 2020 and December 2020 measures were the highest and second-highest implied versus realized spreads in history.

What key strategies were used to manage the Funds during the twelve-month reporting period ended December 31, 2020?

Nuveen S&P 500 Buy-Write Income Fund (BXMX)

BXMX (or the Fund) seeks attractive total return with less volatility than the S&P 500^® Index. During the twelve-month reporting period ended December 31, 2020, the Fund invested in an equity portfolio which sought to track the total return of the S&P 500^® Index and wrote (sold) listed index call options on approximately 100% of the notional value of its stock portfolio. The cash premium generated by the index call options is intended to supplement the dividend yield on the underlying stock portfolio to support the Fund’s distribution policy and to provide the potential for growth in value during rising markets and/or risk mitigation in the event of a market decline.

The writing of index call options on a broad equity index, while investing in a portfolio of equities, has the potential to enhance the BXMX’s risk-adjusted returns while exposing the Fund to less risk than unhedged equity investments. Hedging the equity portfolio with index call options may limit the Fund’s participation in market advances in exchange for the cash premium received for the written index call options. In addition, market declines are typically buffered by the amount of the cash premium received by the Fund. In flat or declining markets, BXMX’s call option premium can potentially enhance total return relative to the S&P 500^® Index. In rising markets, the call options may reduce the Fund’s total return relative to the S&P 500^® Index.

Nuveen Dow 30^SM Dynamic Overwrite Fund (DIAX)

DIAX (or the Fund) seeks attractive total return with less volatility than the Dow Jones Industrial Average (DJIA). NAM varies the level of call option overwrite within a range of approximately 35% to 75%, with a long-run target of 55% overwrite. NAM uses its proprietary view of the market’s return and volatility profile to dynamically adjust the overwrite percentage and other factors. Generally, if NAM expects the equity market to appreciate, the overwrite percentage will be reduced to offer more potential upside capture. Likewise, if NAM expects equity markets to be flat or to decline, the overwrite percentage may be increased, thus managing the Fund to potentially receive additional cash flow from higher sales of call options. This dynamic option overwrite approach offers potential for greater equity market upside capture than the full overwrite approach, while still offering a measure of downside risk management. The Fund currently expects to carry out its principal investment strategy by emphasizing options on broad-based indexes, individual stocks in the DJIA, and options on custom baskets of stocks in addition to exchange-traded funds (ETFs). The Fund also has the opportunity to utilize call spread strategies and sell put options on a portion of the underlying equity portfolio.

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Portfolio Managers’ Comments (continued)

For the Fund’s equity portfolio, NAM fully replicates the DJIA.

Nuveen S&P 500 Dynamic Overwrite Fund (SPXX)

SPXX (or the Fund) seeks attractive total return with less volatility than the S&P 500^® Index. NAM varies the level of option overwrite within a range of approximately 35% to 75% overwrite, with a long-run target of 55% overwrite. NAM uses its proprietary view of the market’s return and volatility profile to dynamically adjust the overwrite percentage and other factors.

Generally, if NAM expects the equity market to appreciate, the overwrite percentage will be reduced to offer more potential upside capture. Likewise, if NAM expects equity markets to be flat or to decline, the overwrite percentage may be increased, thus managing the Fund to potentially receive additional cash flow from higher sales of call options. This dynamic option overwrite approach offers potential for greater equity market upside capture than the full overwrite approach, while still offering a measure of downside risk management. The Fund currently expects to emphasize index call options on the S&P 500^® Index and can also employ an expanded range of options including index options on other broad-based indexes and options on custom baskets of stocks in addition to single name options. The Fund also has the opportunity to utilize call spread strategies and sell put options on a portion of the underlying equity portfolio.

NAM uses a quantitative process to construct the equity portfolio for SPPX. The model evaluates approximately 3,000 domestic and non-U.S. stocks to construct a portfolio of 200 to 400 stocks selected to match the risk characteristics of the S&P 500^® Index, to the extent possible, while giving consideration to criteria and constraints established by NAM. Portfolio parameters may include, but are not limited to: tracking error of the portfolio to the S&P 500^® Index, and overlap of holdings with the S&P 500^® Index. In addition, NAM will consider the tax consequences of certain transactions within the equity portfolio and intends to manage the portfolio in a tax-efficient manner by taking, for example, capital losses when possible to offset realized capital gains. NAM will rebalance and adjust the equity portfolio as necessary for tracking and tax management purposes.

Nuveen Nasdaq 100 Dynamic Overwrite Fund (QQQX)

QQQX (or the Fund) seeks attractive total return with less volatility than the Nasdaq-100 Index. NAM varies the level of call option overwrite within a range of approximately 35% to 75% overwrite, with a long-run target of 55% overwrite. NAM uses its proprietary view of the market’s return and volatility profile to dynamically adjust the overwrite percentage and other factors. Generally, if NAM expects the equity market to appreciate, the overwrite percentage will be reduced to offer more potential upside capture. Likewise, if NAM expects equity markets to be flat or to decline, the overwrite percentage may be increased, thus managing the Fund to potentially receive additional cash flow from higher sales of call options. This dynamic option overwrite approach offers potential for greater equity market upside capture than the full overwrite approach, while still offering a measure of downside risk management. The Fund, in carrying out its principal options strategy, expects to primarily write index call options on the Nasdaq-100 Index and other broad-based indexes and can also write call options on a variety of other equity market indexes and options on custom baskets of stocks in addition to single name options. The Fund also has the opportunity to utilize call spread strategies and sell put options on a portion of the underlying equity portfolio.

NAM uses a quantitative process to construct the equity portfolio for QQQX. The model evaluates approximately 3,000 domestic and non-U.S. stocks to construct a portfolio of 100 to 200 stocks selected to match the risk characteristics of the Nasdaq-100 Index, to the extent possible, while giving consideration to criteria and constraints established by NAM. Portfolio parameters may include, but are not limited to: tracking error of the portfolio to the Nasdaq-100 Index, and overlap of holdings with the Nasdaq-100 Index. In addition, NAM will consider the tax consequences of certain transactions within the equity portfolio and intends to manage the portfolio in a tax-efficient manner by taking, for example, capital losses when possible to offset realized capital gains. NAM will rebalance and adjust the equity portfolio as necessary for tracking and tax management purposes.

8

How did the Funds perform during the twelve-month reporting period ended December 31, 2020?

The tables in the Performance Overview and Holding Summaries section of this report provide total returns at net asset value (NAV) for the period ended December 31, 2020. Each Fund’s total returns at NAV are compared with the performance of its corresponding market index and, as available, a secondary custom blended benchmark.

For the twelve-month reporting period ended December 31, 2020, BXMX’s shares at NAV outperformed the Cboe S&P 500^® BuyWrite Index (BXM^SM), its primary index.

DIAX underperformed the Dow Jones Industrial Average and its secondary index, the DIAX Blended Benchmark, which is a blended return consisting of 1) 55% Cboe DJIA BuyWrite Index (BXD^SM) and 2) 45% Dow Jones Industrial Average. SPXX underperformed the S&P 500^® Index, but outperformed its secondary index the SPXX Blended Benchmark, which is a blended return consisting of 1) 55% the Cboe S&P 500^® BuyWrite Index (BXM^SM) and 2) 45% the S&P 500^® Index. QQQX underperformed the Nasdaq-100 Index and its secondary index, the QQQX Blended Benchmark, which is a blended return consisting of 1) 55% Cboe Nasdaq 100 BuyWrite Index (BXN^SM) and 2) 45% Nasdaq-100^® Index. Each Fund’s Blended Benchmark is described further in the Glossary of Terms Used in this Report.

Nuveen S&P 500 Buy-Write Income Fund (BXMX)

Active index call writing generated risk-mitigating cash flow for the Fund throughout the twelve-month period. In achieving its low-volatility objective, the measured risk of the Fund was lower than that of the U.S. equity market and the BXM^SM, as its standard deviation of daily returns for 2020 was 23.74%, versus 34.43% and 27.01% for the S&P 500^® Index and the BXM^SM, respectively. The Fund exhibited a beta to the BXM^SM of 0.85 for the reporting period. Additionally, the Fund’s active approach to index call writing contributed positively to the Fund’s returns during the equity market’s steep bear market decline in the first quarter of 2020, and during the smaller equity pullback in September and October 2020.

The index call options written by the Fund often have similar characteristics to the index call options present in the BXM^SM at any given time. However, unlike the BXM^SM, the Fund employs an active strategy that gives its portfolio management team discretion to diversify expiration dates and strike prices across a portfolio of index call options, and to opportunistically pursue attractive call premiums while maintaining a relatively consistent risk profile. This approach led to the Fund’s outperformance relative to the BXM^SM for the reporting period as well as during the first, second, and fourth quarters 2020. Specifically, during the first quarter 2020, the Fund’s active approach generated higher cash flow from written index call options and lower market exposure, relative to its benchmark as the cash flow generated by the BXM^SM was limited to one index call option written just prior to the equity market decline and one index call option written during the decline. Additionally, the passive approach of the BXM^SM resulted in increasing market exposure as the equity market fell. The Fund’s active approach also added value over the BXM^SM during the second and fourth quarters 2020 as the Fund experienced fewer written call option losses than the BXM^SM by making several index call option trades to increase cash flow and maintain relatively consistent equity market exposure as the market advanced. During these periods the BXM^SM’s passive, single contract approach resulted in lower market exposure and less cash flow over the course of the market’s advances.

Writing index call options limited equity market participation, generally detracting from the Fund’s return in the second, third and fourth quarters of 2020, consistent with expectations during periods when the equity market advances at an above average rate. The Fund’s underperformance, relative to the BXM^SM, in the third quarter 2020 was primarily due to a larger loss than the BXM^SM for the month of September 2020. Consistent with its active approach, the Fund began September 2020 with the weighted-average strike price of its written index call option portfolio approximately at-the-money, resulting in relatively more exposure to the market’s decline than the BXM^SM, which began the month with very low market exposure as the strong market advance in August 2020 put its written index call option deep in-the-money.

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Portfolio Managers’ Comments (continued)

Nuveen Dow 30^SM Dynamic Overwrite Fund (DIAX)

DIAX’s call option strategy is expected to dampen the beta (a measure of price volatility) of the overall portfolio. Active index call writing generated risk-reducing cash flow throughout the reporting period. In attempting to achieve its low volatility objective, the Fund’s annualized standard deviation of daily returns for the reporting period was 32.45% compared to 36.78% and 30.39% for Dow Jones Industrial Average and the secondary index, which is a blend of 55% Cboe DJIA BuyWrite Index (BXD^SM) and 45% Dow Jones Industrial Average, respectively. This overwrite strategy provides incremental cash flow to the Fund and allows the portion of the Fund’s assets that are not overwritten to participate in any equity market rally. Those portions of the Fund that are overwritten have capped upside potential. The downside is buffered by the amount of cash flow premium received. Therefore, in flat or declining markets, the option premiums can enhance total returns relative to the Index. In rising markets, however, the options can hinder the Fund’s total return relative to the Index.

It is important to note the relationship between the market’s implied volatility that is measured by the Chicago Board Options Exchange (Cboe) Volatility Index^® (the “VIX^®”), and option writing. Implied volatility is a component of an option itself. It is the estimated volatility of an asset underlying an option. Higher implied volatilities result in higher option prices. The same can be said about the implied volatility of the market.

During the first half of the reporting period, equity markets, including the Index, rapidly sold off in February 2020, reaching bear market territory (a 20% drop from the previous high) within three weeks, the fastest bear market decline in history. During the first half of the reporting period, the VIX^® averaged 32.87, well above its historical average of 19.24. The VIX^® rose as high as 85.47 on March 18, 2020, just shy of its all-time intra-day high reading of 89.53 set in 2008. The VIX^® ended the reporting period at 22.75.

In the second half of the reporting period, NAM took a more dynamic approach to the overwrite strategy. We maintained an approximate 58% overwrite but had periods where the overwrite was as low as 38% and other times where it reached nearly 71%, which is above its long-term target of 55%. During the second half of the reporting period, the VIX^® averaged 30.43, well above its historical average of 19.24 and we took advantage of the VIX’s volatility to add new positions. We also bought and sold call options on single name positions, added strangle positions which involved selling a call and a put option on an index, and added a limited number of put options as the markets rebounded.

Several factors contributed to performance. NAM bought and sold options on single-name positions, including American Express Co, Walmart Inc, Chevron Corp, Johnson & Johnson, eBay Inc, Pfizer Inc and Merck & Co Inc, which contributed to performance. In both instances, the Fund was able to take advantage of the higher levels of volatility and capture additional option premium income. During the fourth quarter 2020, the portfolio management team made several tactical trades selling short-term call options, which contributed to performance. NAM also sold put options, which also contributed to performance. In periods of rising equity markets, consistently selling put options helps to generate additional income as these obligations expire worthless. Selling puts generates immediate portfolio income which the Fund maintains when the put expires out-of-the-money. Lastly, the Fund’s call writing strategy provided some risk mitigation during the sell-off in February, March, September and October 2020.

Several factors influenced the Fund’s underperformance. The February 2020 options contract expiration and roll came just prior to the shift in market volatility. Call options written by the Fund in February 2020 provided relatively modest downside protection compared to equity losses through the market sell-off. This was exacerbated by the March 2020 expiration date being closely aligned with the market bottom. Writing near-the-money call options limited upside participation in the partial recovery at the end of the March 2020. The sudden shift from a low- to high-volatility environment and the timing of the Fund’s options contract expirations had a significant impact on the Fund’s return during the reporting period. In addition, NAM wrote call options on the Russell 2000^® Index which detracted from performance during the second half of the reporting period. The Russell 2000^® Index rallied sharply during the reporting period. As a result, the Fund collected less premium income as it unwound positions in the index at higher prices than

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was originally received in premium. NAM also wrote S&P 500^® Index options rather than those based on the narrower DJIA. During the fourth quarter 2020, the S&P 500^® Index outperformed the DJIA which resulted in more premium being spent to close the positions at expiration. Lastly, the Fund was not able to fully participate in the equity market advances as the upside potential was capped due to the overwrite strategy.

The equity portfolio of DIAX fully replicates the DJIA and thus contributes no return differential to the Fund’s benchmark, the DJIA.

Nuveen S&P 500 Dynamic Overwrite Fund (SPXX)

SPXX’s call option strategy is expected to dampen the beta (a measure of price volatility) of the overall portfolio. Active index call writing generated risk-reducing cash flow throughout the reporting period. In attempting to achieve its low volatility objective, the Fund’s annualized standard deviation of daily returns for the reporting period was 30.59% compared to 34.44% and 29.67% for the S&P 500^® Index and its secondary index, which is a blend of 55% the Cboe S&P 500^® BuyWrite Index (BXM^SM) and 45% the S&P 500^® Index, respectively. This overwrite strategy provides incremental cash flow to the Fund and allows the portion of the Fund’s assets that are not overwritten to participate in any equity market rally. Those portions of the Fund that are overwritten have capped upside potential. The downside is buffered by the amount of cash flow premium received. Therefore, in flat or declining markets, the option premiums can enhance total returns relative to the index. In rising markets, however, the options can hinder the Fund’s total return relative to the index.

It is important to note the relationship between market’s implied volatility that is measured by the Chicago Board Options Exchange (Cboe) Volatility Index^® (the “VIX^®”), and option writing. Implied volatility is a component of an option itself. It is the estimated volatility of an asset underlying an option. Higher implied volatilities result in higher option prices. The same can be said about the implied volatility of the market.

During the first half of the reporting period, equity markets, including the Index, rapidly sold off in February 2020, reaching bear market territory (a 20% drop from the previous high) within three weeks – the fastest bear market decline in history. Over the first half of the reporting period, the Index reached a high on February 19, 2020 and declined 34% to its low on March 23, 2020. During the first half of the reporting period, the VIX^® averaged 32.87, well above its historical average of 19.24. The VIX^® rose as high as 85.47 on March 18, 2020, just shy of its all-time intra-day high reading of 89.53 set in 2008. The VIX^® ended the reporting period at 22.75.

During the second half of the reporting period, NAM took a more dynamic approach to the overwrite strategy and maintained an approximate 58% overwrite but had periods where the overwrite was a low as 38% and other times where it reached nearly 71%, which is above its long-term target of 55%. During the second half of the reporting period, the VIX^® averaged 30.43, well above its historical average of 19.24, allowing the portfolio management team to take advantage of the VIX^®’s volatility to add new positions. NAM also bought and sold call options on single name positions, added strangle positions which involved selling a call and a put option on an index, and added a limited number of put options as the markets rebounded.

Several factors contributed to performance. NAM bought and sold options on single-name positions, including American Express Co, Walmart Inc, Chevron Corp, Johnson & Johnson, eBay Inc, Pfizer Inc and Merck & Co Inc., which contributed to performance. In both instances, the Fund was able to take advantage of the higher levels of volatility and capture additional option premium income. During the fourth quarter 2020, the team made several tactical trades selling short-term call options, which contributed to performance. NAM also sold put options, which contributed to performance. In periods of rising equity markets, consistently selling put options helps to generate additional income as these obligations expire worthless. Selling puts generates immediate portfolio income which the Fund maintains when the put expires out-of-the-money. Lastly, the Fund’s call writing strategy provided some risk mitigation during the sell-off in February, March, September and October 2020.

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Portfolio Managers’ Comments (continued)

Several factors influenced the Fund’s underperformance. The February 2020 options contract expiration and roll came just prior to the shift in market volatility. Call options written by the Fund in February 2020 provided relatively modest downside protection compared to equity losses through the market sell-off. This was exacerbated by the March 2020 expiration date being closely aligned with the market bottom. Writing near-the-money call options limited upside participation in the partial recovery at the end of the March 2020. The sudden shift from a low- to high-volatility environment and the timing of the Fund’s options contract expirations had a significant impact on the Fund’s return during the reporting period. In addition, NAM wrote call options on the Russell 2000^® Index which detracted from performance during the second half of the reporting period. The Russell 2000^® Index rallied sharply during the reporting period. As a result, the Fund collected less premium income as it unwound positions in the index at higher prices than was originally received in premium. Lastly, the Fund was not able to fully participate in the equity market advances as the upside potential was capped due to the overwrite strategy.

The equity portion of SPPX is quantitatively managed utilizing the investment process described above. The investment performance is primarily driven by the quantitative investment process, special criteria constraints and tax considerations established by NAM. NAM does not make active decision based upon market conditions, individual stocks, sector selection, country allocation, etc.

Nuveen Nasdaq 100 Dynamic Overwrite Fund (QQQX)

QQQX’s call option strategy is expected to dampen the beta (a measure of price volatility) of the overall portfolio. Active index call writing generated risk-reducing cash flow throughout the reporting period. In attempting to achieve its low volatility objective, the Fund’s annualized standard deviation of daily returns for the reporting period was 31.54% compared to 36.39% and 23.34% for the Nasdaq-100 Index 30.78% and its secondary index, which is a blend of 55% Cboe Nasdaq 100 BuyWrite Index (BXN^SM) and 45% Nasdaq-100 Index, respectively. This overwrite strategy provides incremental cash flow to the Fund and allows the portion of the Fund’s assets that are not overwritten to participate in any equity market rally. Those portions of the Fund that are overwritten have capped upside potential. The downside is buffered by the amount of cash flow premium received. Therefore, in flat or declining markets, the option premiums can enhance total returns relative to the Index. In rising markets, however, the options can hinder the Fund’s total return relative to the index.

It is important to note the relationship between market’s implied volatility that is measured by the Chicago Board Options Exchange (Cboe) Volatility Index^® (the “VIX^®”), and option writing. Implied volatility is a component of an option itself. It is the estimated volatility of an asset underlying an option. Higher implied volatilities result in higher option prices. The same can be said about the implied volatility of the market.

During the first half of the reporting period, equity markets, including the S&P 500^® Index, rapidly sold off in February 2020, reaching bear market territory (a 20% drop from the previous high) within three weeks, the fastest bear market decline in history. During the first half of the reporting period, the VIX^® averaged 32.87, well above its historical average of 19.24, The VIX^® rose as high as 85.47 on March 18, 2020, just shy of its all-time intra-day high reading of 89.53 set in 2008. The VIX^® ended the reporting period at 22.75.

In the second half of the reporting period, NAM took a more dynamic approach to the overwrite strategy and maintained an approximate 58% overwrite but had periods where the overwrite was a low as 38% and other times where it reached nearly 71%, which is above its long-term target of 55%. During the second half of the reporting period, the VIX^® averaged 30.43, well above its historical average of 19.24 and we took advantage of the VIX^®’s volatility to add new positions. NAM also bought and sold call options on single name positions, added strangle positions which involved selling a call and a put option on an index, and added a limited number of put options as the markets rebounded.

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Several factors contributed to performance. NAM bought and sold options on single-name positions, including American Express Co, Walmart Inc, Chevron Corp, Johnson & Johnson, eBay Inc, Pfizer Inc and Merck & Co Inc. These positions contributed to performance. In both instances, the Fund was able to take advantage of the higher levels of volatility and capture additional option premium income. During the fourth quarter 2020, the team made several tactical trades selling short-term call options, which contributed to performance. NAM also sold put options, which also contributed to performance. In periods of rising equity markets, consistently selling put options helps to generate additional income as these obligations expire worthless. Selling puts generates immediate portfolio income which the Fund maintains when the put expires out-of-the-money. Lastly, the Fund’s call writing strategy provided some risk mitigation during the sell-off in February, March, September and October 2020.

Several factors influenced the Fund’s underperformance. The February 2020 options contract expiration and roll came just prior to the shift in market volatility. Call options written by the Fund in February 2020 provided relatively modest downside protection compared to equity losses through the market sell-off. This was exacerbated by the March 2020 expiration date being closely aligned with the market bottom. Writing near-the-money call options limited upside participation in the partial recovery at the end of the March 2020. The sudden shift from a low- to high-volatility environment and the timing of the Fund’s options contract expirations had a significant impact on the Fund’s return during the reporting period. In addition, NAM wrote call options on the Russell 2000^® Index which detracted from performance during the second half of the reporting period. The Russell 2000^® Index rallied sharply during the reporting period. As a result, the Fund collected less premium income as it unwound positions in the index at higher prices than was originally received in premium. Lastly, the Fund was not able to fully participate in the equity market advances as the upside potential was capped due to the overwrite strategy.

The equity portion of QQQX is quantitatively managed utilizing the investment process described above. The investment performance is primarily driven by the quantitative investment process, special criteria constraints and tax considerations established by NAM. NAM does not make active decision based upon market conditions, individual stocks, sector selection, country allocation, etc.

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Common Share Information

DISTRIBUTION INFORMATION

The following 19(a) Notice presents the Funds’ most current distribution information as of November 30, 2020 as required by certain exempted regulatory relief the Funds have received.

Because the ultimate tax character of your distributions depends on the Funds’ performance for its entire fiscal year (which is the calendar year for the Funds) as well as certain fiscal year-end (FYE) tax adjustments, estimated distribution source information you receive with each distribution may differ from the tax information reported to you on your Funds’ IRS Form 1099 statement.

DISTRIBUTION INFORMATION – AS OF NOVEMBER 30, 2020

This notice provides shareholders with information regarding fund distributions, as required by current securities laws. You should not draw any conclusions about the Funds’ investment performance from the amount of this distribution or from the terms of the Funds’ Managed Distribution Policy.

Each Fund may in certain periods distribute more than its income and net realized capital gains, and the Funds currently estimate that they have done so for the fiscal year-to-date period. In such instances, a portion of the distribution may be a return of capital. A return of capital may occur, for example, when some or all of the money that you invested in the Fund is paid back to you. A return of capital distribution does not necessarily reflect the Funds’ investment performance. For example, if a Fund generates a positive total return during a reporting period that is commensurate with its distribution rate, and realizes net gains by selling portfolio securities, a substantial portion of its distribution will likely be characterized as capital gains; but if the Fund generated such commensurate returns but instead did not realize net gains by selling portfolio securities during that period, then a substantial portion of its distributions in most cases would largely be characterized as a “return of capital”, despite the fact that the distributions were commensurate with those positive returns. Neither a capital gain distribution nor a return of capital distribution should be confused with “yield” or “income.”

The amounts and sources of distributions set forth below are only estimates and are not being provided for tax reporting purposes. The actual amounts and sources of the amounts for tax reporting purposes will depend upon the Funds’ investment experience during the remainder of its fiscal year and may be subject to changes based on tax regulations. Each Fund will send you a Form 1099-DIV for the calendar year that will tell you how to report these distributions for federal income tax purposes. More details about the Funds’ distributions and the basis for these estimates are available on www.nuveen.com/cef.

The following table provides estimates of the Funds’ distribution sources, reflecting year-to-date cumulative experience through the latest month-end. Each Fund attributes these estimates equally to each regular distribution throughout the year. Consequently, the estimated information shown below is for the current distribution, and also represents an updated estimate for all prior months in the year.

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The following table provides information regarding the Funds’ distributions and total return performance over various time periods. This information is intended to help you better understand whether returns for the specified time periods were sufficient to meet distributions.

DISTRIBUTION INFORMATION – AS OF DECEMBER 31, 2020

The following tables provide information regarding the Funds’ common share distributions and total return performance for the fiscal year ended December 31, 2020. This information is intended to help you better understand whether the Funds’ returns for the specified time period were sufficient to meet its distributions.

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NUVEEN CLOSED-END FUND DISTRIBUTION AMOUNTS

The Nuveen Closed-End Funds’ monthly and quarterly periodic distributions to shareholders are posted on www.nuveen.com and can be found on Nuveen’s enhanced closed-end fund resource page, which is at https://www.nuveen.com/resource-center-closed-end-funds, along with other Nuveen closed-end fund product updates. To ensure timely access to the latest information, shareholders may use a subscribe function, which can be activated at this web page (https://www.nuveen.com/subscriptions).

COMMON SHARE EQUITY SHELF PROGRAMS

During the current reporting period, the Funds were authorized by the Securities and Exchange Commission to issue additional common shares through an equity shelf program (Shelf Offering). Under these programs, the Funds, subject to market conditions, may raise additional capital from time to time in varying amounts and offering methods at a net price at or above each Fund’s NAV per common share. The total amount of common shares authorized under these Shelf Offerings are as shown in the accompanying table.

During the current reporting period, the Funds sold common shares through their Shelf Offerings at a weighted average premium to their NAV per common share as shown in the accompanying table.

Refer to Notes to Financial Statements, Note 5 – Fund Shares for further details of Shelf Offerings and each Fund’s respective transactions.

COMMON SHARE REPURCHASES

During August 2020, the Funds’ Board of Trustees reauthorized an open-market share repurchase program, allowing each Fund to repurchase an aggregate of up to approximately 10% of its outstanding common shares.

As of December 31, 2020, and since the inception of the Funds’ repurchase programs, the Funds have cumulatively repurchased and retired their outstanding common shares as shown in the accompanying table.

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During the current reporting period, the Funds did not repurchase any of their outstanding common shares.

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Refer to the Glossary of Terms Used in this Report for further definition of the terms used within this section.

Past performance is not predictive of future results. Current performance may be higher or lower than the data shown. Returns do not reflect the deduction of taxes that shareholders may have to pay on Fund distributions or upon the sale of Fund shares. Returns at NAV are net of Fund expenses, and assume reinvestment of distributions. Comparative index return information is provided for the Fund’s shares at NAV only. Indexes are not available for direct investment.

Common Share Price Performance — Weekly Closing Price

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This data relates to the securities held in the Fund’s portfolio of investments as of the end of the reporting period. It should not be construed as a measure of performance for the Fund itself. Holdings are subject to change.

(% of total long-term investments)

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Refer to the Glossary of Terms Used in this Report for further definition of the terms used within this section.

Past performance is not predictive of future results. Current performance may be higher or lower than the data shown. Returns do not reflect the deduction of taxes that shareholders may have to pay on Fund distributions or upon the sale of Fund shares. Returns at NAV are net of Fund expenses, and assume reinvestment of distributions. Comparative index return information is provided for the Fund’s shares at NAV only. Indexes are not available for direct investment.

Common Share Price Performance — Weekly Closing Price

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This data relates to the securities held in the Fund’s portfolio of investments as of the end of the reporting period. It should not be construed as a measure of performance for the Fund itself. Holdings are subject to change.

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Refer to the Glossary of Terms Used in this Report for further definition of the terms used within this section.

Performance prior to December 22, 2014, reflects the Fund’s performance under the management of a sub-adviser using an investment strategy that differed from those currently in place.

Past performance is not predictive of future results. Current performance may be higher or lower than the data shown. Returns do not reflect the deduction of taxes that shareholders may have to pay on Fund distributions or upon the sale of Fund shares. Returns at NAV are net of Fund expenses, and assume reinvestment of distributions. Comparative index return information is provided for the Fund’s shares at NAV only. Indexes are not available for direct investment.

Common Share Price Performance — Weekly Closing Price

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This data relates to the securities held in the Fund’s portfolio of investments as of the end of the reporting period. It should not be construed as a measure of performance for the Fund itself. Holdings are subject to change.

(% of total long-term investments)

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Refer to the Glossary of Terms Used in this Report for further definition of the terms used within this section.

Past performance is not predictive of future results. Current performance may be higher or lower than the data shown. Returns do not reflect the deduction of taxes that shareholders may have to pay on Fund distributions or upon the sale of Fund shares. Returns at NAV are net of Fund expenses, and assume reinvestment of distributions. Comparative index return information is provided for the Fund’s shares at NAV only. Indexes are not available for direct investment.

Common Share Price Performance — Weekly Closing Price

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This data relates to the securities held in the Fund’s portfolio of investments as of the end of the reporting period. It should not be construed as a measure of performance for the Fund itself. Holdings are subject to change.

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