UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number: 811-04791

AB MUNICIPAL INCOME FUND, INC.

(Exact name of registrant as specified in charter)

1345 Avenue of the Americas, New York, New York 10105

(Address of principal executive offices) (Zip code)

Joseph J. Mantineo

AllianceBernstein L.P.

1345 Avenue of the Americas

New York, New York 10105

(Name and address of agent for service)

Registrant’s telephone number, including area code: (800) 221-5672

Date of fiscal year end: May 31, 2021

Date of reporting period: November 30, 2020

ITEM 1.    REPORTS TO STOCKHOLDERS.

NOV    ^11.30.20

SEMI-ANNUAL REPORT

AB MUNICIPAL INCOME FUND

As of January 1, 2021, as permitted by new regulations adopted by the Securities and Exchange Commission, each Fund’s annual and semi-annual shareholder reports are no longer sent by mail, unless you specifically requested paper copies of the reports. Instead, the reports are made available on a website, and you will be notified by mail each time a report is posted and provided with a website address to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications from a Fund electronically at any time by contacting your financial intermediary (such as a broker-dealer or bank) or, if you are a direct investor, by calling the Fund at (800) 221 5672.

You may elect to receive all future reports in paper form free of charge. If you invest through a financial intermediary, you can contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports; if you invest directly with a Fund, you can call the Fund at (800) 221 5672. Your election to receive reports in paper form will apply to all funds held in your account with your financial intermediary or, if you invest directly, to all AB Mutual Funds you hold.

Investors should consider the investment objectives, risks, charges and expenses of the Fund carefully before investing. For copies of our prospectus or summary prospectus, which contain this and other information, visit us online at www.abfunds.com or contact your AB representative. Please read the prospectus and/or summary prospectus carefully before investing.

This shareholder report must be preceded or accompanied by the Fund’s prospectus for individuals who are not current shareholders of the Fund.

You may obtain a description of the Fund’s proxy voting policies and procedures, and information regarding how the Fund voted proxies relating to portfolio securities during the most recent 12-month period ended June 30, without charge. Simply visit AB’s website at www.abfunds.com, or go to the Securities and Exchange Commission’s (the “Commission”) website at www.sec.gov, or call AB at (800) 227 4618.

The Fund files its complete schedule of portfolio holdings with the Commission for the first and third quarters of each fiscal year as an exhibit to its reports on Form N-PORT. The Fund’s Form N-PORT reports are available on the Commission’s website at www.sec.gov. The Fund’s Forms N-PORT may also be reviewed and copied at the Commission’s Public Reference Room in Washington, DC; information on the operation of the Public Reference Room may be obtained by calling (800) SEC 0330. AB publishes full portfolio holdings for the Fund monthly at www.abfunds.com.

AllianceBernstein Investments, Inc. (ABI) is the distributor of the AB family of mutual funds. ABI is a member of FINRA and is an affiliate of AllianceBernstein L.P., the Adviser of the funds.

The [A/B] logo is a registered service mark of AllianceBernstein and AllianceBernstein^® is a registered service mark used by permission of the owner, AllianceBernstein L.P.

FROM THE PRESIDENT

Dear Shareholder,

We are pleased to provide this report for AB Municipal Income Fund: AB California Portfolio, AB High Income Municipal Portfolio, AB National Portfolio and AB New York Portfolio (each a “Portfolio,” and collectively, the “Portfolios”). Please review the discussion of Portfolio performance, the market conditions during the reporting period and the Portfolios’ investment strategies.

As always, AB strives to keep clients ahead of what’s next by:

Whether you’re an individual investor or a multi-billion-dollar institution, we put knowledge and experience to work for you.

AB’s global research organization connects and collaborates across platforms and teams to deliver impactful insights and innovative products. Better insights lead to better opportunities—anywhere in the world.

For additional information about AB’s range of products and shareholder resources, please log on to www.abfunds.com.

Thank you for your investment in the AB Mutual Funds.

Sincerely,

Robert M. Keith

President and Chief Executive Officer, AB Mutual Funds

SEMI-ANNUAL REPORT

January 12, 2021

This report provides management’s discussion of fund performance for AB Municipal Income Fund: AB California Portfolio, AB High Income Municipal Portfolio, AB National Portfolio and AB New York Portfolio for the semi-annual reporting period ended November 30, 2020.

The investment objective of the California, National and New York Portfolios is to earn the highest level of current income, exempt from federal income tax, and in the case of the California and New York Portfolios, state taxation of the respective state, that is available without assuming what the Adviser considers to be undue risk to principal or income. The investment objective of the High Income Municipal Portfolio is to earn the highest level of current income, exempt from federal income tax, that is available consistent with what the Adviser considers to be an appropriate level of risk.

NAV RETURNS AS OF NOVEMBER 30, 2020 (unaudited)

NAV RETURNS AS OF NOVEMBER 30, 2020 (unaudited)

INVESTMENT RESULTS

The preceding tables show performance for each Portfolio compared to its benchmark, the Bloomberg Barclays Municipal Bond Index, for the six- and 12-month periods ended November 30, 2020.

All share classes of the Portfolios outperformed the benchmark for the six-month period, but underperformed for the 12-month period, before sales charges. During the six-month period, an overweight to municipal credit contributed, relative to the benchmark, as credit rebounded from March lows. For the 12-month period, an overweight to municipal credit detracted, following the sell-off in March.

California: During both periods, security selection within the public-education sector contributed, relative to the benchmark, while selection in multi-family housing detracted. During the six-month period, security selection in private higher education contributed. During the 12-month period, security selection in miscellaneous revenue detracted, while selection in local general obligation (“GO”) bonds and toll roads/transit contributed.

High Income: While the benchmark is fully invested in investment-grade securities, the Portfolio invests in below-investment-grade securities, which was beneficial over the six-month period but detrimental over the 12-month period. During the six-month period, security selection within the special-tax and state-GO sectors contributed, while selection in multi-family housing detracted. For the 12-month period, security selection in

miscellaneous revenue and private higher education detracted, while selection in tobacco securitization and public education contributed.

National: During both periods, security selection within the multi-family housing sector detracted. For the six-month period, security selection in state GO and special tax contributed. During the 12-month period, security selection in state GO detracted, while selection in toll roads/transit contributed.

New York: During the six-month period, security selection within the special-tax and industrial-development airline sectors contributed, while selection in tax-supported state lease detracted. For the 12-month period, security selection in special tax and industrial development miscellaneous revenue detracted, while selection in airports/ports contributed.

All Portfolios utilized derivatives in the form of inflation Consumer Price Index (“CPI”) swaps and interest rate swaps for hedging purposes. During both periods, inflation CPI swaps added to absolute returns for all Portfolios. During the 12-month period, interest rate swaps added for all Portfolios. During the six-month period, interest rate swaps had an immaterial impact for the National and New York Portfolios, added for the California Portfolio and detracted for the High Income Municipal Portfolio.

The High Income Municipal Portfolio also utilized credit default swaps for investment purposes, which detracted for both periods.

MARKET REVIEW AND INVESTMENT STRATEGY

Municipal performance over the six-month period ended November 30, 2020, was positive. According to the Federal Reserve Bank of New York, the US economy stopped contracting in early May, and began a steady recovery through the rest of the summer. With respect to monetary policy, the US Federal Reserve (“the Fed”) Board of Governors stated that short-term interest rates were likely to be held at current low levels for the next few years. Consistent with the improving economy and steady monetary policy, municipals regained their footing and have performed exceptionally well following the sharp sell-off in March.

While outflows and a lack of liquidity sparked the sell-off in March, these themes have since largely abated, as investors took comfort in the significant federal support provided to state and local governments. On the monetary side, the Fed established the Municipal Liquidity Facility, which can purchase as much as $500 billion in short-term notes directly from municipalities, helping alleviate near-term liquidity concerns for eligible municipalities. The fiscal side brought issuers additional support in the form of the CARES Act, which included $150 billion to state and local governments, $120 billion to hospitals, $31 billion for education, $25 billion for transportation and $10 billion to airports.

The Portfolios may purchase municipal securities that are insured under policies issued by certain insurance companies. In the past, insured municipal securities typically received a higher credit rating, which meant that the issuer of the securities paid a lower interest rate. As a result of declines in the credit quality and associated downgrades of most bond insurers, insurance has less value than it did in the past. The market now values insured municipal securities primarily based on the credit quality of the issuer of the security, with little value given to the insurance feature. In purchasing such insured securities, the Adviser evaluates the risk and return of municipal securities through its own research. If an insurance company’s rating is downgraded or the company becomes insolvent, the prices of municipal securities insured by the insurance company may decline.

INVESTMENT POLICIES

Each of the California, National and New York Portfolios pursues its objective by investing principally in high-yielding, predominantly investment-grade municipal securities. The High Income Municipal Portfolio pursues its objective by investing principally in high-yielding municipal securities that may be non-investment grade or investment grade.

Each Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax for certain taxpayers. Each of the Portfolios that invests in a named state pursues its objective by investing at least 80% of its net assets in municipal securities issued by the named state or municipal securities with interest that is otherwise exempt from the named state’s income tax. The National Portfolio may invest 25% or more of its net assets in a single state.

The California, National and New York Portfolios may also invest in forward commitments; tender option bonds (“TOBs”); zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.

(continued on next page)

The High Income Municipal Portfolio may invest without limit in lower-rated securities (“junk bonds”), which may include securities having the lowest rating, and in unrated securities that, in the Adviser’s judgment, would be lower-rated securities if rated. The Portfolio may invest in fixed-income securities with any maturity or duration. The Portfolio will seek to increase income for shareholders by investing in longer-maturity bonds. Consistent with its objective of seeking a higher level of income, the Portfolio may experience greater volatility and a higher risk of loss of principal than other municipal funds. The Portfolio may also invest in forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and certain types of mortgage-related securities. The Portfolio may invest in derivatives, such as options, futures contracts, forwards and swaps. The Portfolio may make short sales of securities or maintain a short position and may use other investment techniques. The Portfolio may use leverage for investment purposes to increase income through the use of TOBs and derivative instruments, such as interest rate swaps.

DISCLOSURES AND RISKS

Benchmark Disclosure

The Bloomberg Barclays Municipal Bond Index is unmanaged and does not reflect fees and expenses associated with the active management of a mutual fund portfolio. The Bloomberg Barclays Municipal Bond Index represents the performance of the long-term tax-exempt bond market consisting of investment-grade bonds. An investor cannot invest directly in an index, and its results are not indicative of the performance for any specific investment, including the Portfolios.

A Word About Risk

Market Risk: The value of the Portfolios’ assets will fluctuate as the bond market fluctuates. The value of the Portfolios’ investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events, including public health crises (including the occurrence of a contagious disease or illness), that affect large portions of the market.

Credit Risk: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations.

Below Investment-Grade Securities Risk (High Income Municipal Portfolio): Investments in fixed-income securities with lower ratings (commonly known as “junk bonds”) tend to have a higher probability that an issuer will default or fail to meet its payment obligations. These securities may be subject to greater price volatility due to such factors as specific corporate developments, interest-rate sensitivity and negative performance of the junk bond market generally and may be more difficult to trade than other types of securities.

Municipal Market Risk: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolios’ investments in municipal securities. These factors include economic conditions, political or legislative changes, public health crises, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. To the extent that the Portfolios invest more of their assets in a particular state’s municipal securities, the Portfolios may be vulnerable to events adversely affecting that state, including economic, political and regulatory occurrences, court decisions,

DISCLOSURES AND RISKS (continued)

terrorism public health crises (including the occurrence of a contagious disease or illness) and catastrophic natural disasters, such as hurricanes, fires or earthquakes. For example, the novel coronavirus (COVID-19) pandemic has significantly stressed the financial resources of many issuers of municipal securities, which could impair any such issuer’s ability to meet its financial obligations when due and adversely impact the value of its securities held by the Portfolios. As the full effects of the COVID-19 pandemic on state and local economies and on issuers of municipal securities are still uncertain, the financial difficulties of issuers of municipal securities may continue or worsen, adversely affecting the performance of the Portfolios. The Portfolios’ investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project’s ability to make payments of principal and interest on these securities.

Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the US federal income tax treatment of certain types of municipal securities.

The Portfolios invest from time to time in municipal securities of issuers in Puerto Rico or other US territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other US issuers of municipal securities. Like many US states and municipalities, Puerto Rico experienced a significant downturn during the 2007-2009 recession. Puerto Rico’s downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment, including as a result of the COVID-19 pandemic. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

Tax Risk: There is no guarantee that the income on the Portfolios’ municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the US government and the US Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolios by increasing taxes on that income. In such event, the Portfolios’ net asset value (“NAV”) could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or antici-

DISCLOSURES AND RISKS (continued)

pated actions affecting the tax-exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolios or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolios would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolios’ yield.

Interest-Rate Risk: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest-rate risk is generally greater for fixed-income securities with longer maturities or durations. Very low or negative interest rates would likely magnify the risks associated with changes in interest rates. During periods of very low or negative rates, the Portfolios’ returns would likely be adversely affected.

Duration Risk: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

Inflation Risk: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolios’ assets can decline as can the value of the Portfolios’ distributions. This risk is significantly greater for fixed-income securities with longer maturities.

Leverage Risk (High Income Municipal Portfolio): To the extent the Portfolio uses leveraging techniques, such as TOBs, its NAV may be more volatile because leverage tends to exaggerate the effect of changes in interest rates and any increase or decrease in the value of the Portfolio’s investments.

Illiquid Investments Risk: Illiquid investments risk exists when certain investments are or become difficult to purchase or sell. Difficulty in selling such investments may result in sales at disadvantageous prices affecting the value of your investment in the Portfolios. Causes of illiquid investments risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Illiquid investments risk may be higher in a rising interest-rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more illiquid investments risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

DISCLOSURES AND RISKS (continued)

Derivatives Risk: Derivatives may be difficult to price or unwind and leveraged so that small changes may produce disproportionate losses for the Portfolios. Derivatives, especially over-the-counter derivatives, are also subject to counterparty risk.

Management Risk: The Portfolios are subject to management risk because they are actively managed investment funds. The Adviser will apply its investment techniques and risk analyses in making investment decisions, but there is no guarantee that its techniques will produce the intended results. Some of these techniques may incorporate, or rely upon, quantitative models, but there is no guarantee that these models will generate accurate forecasts, reduce risk or otherwise perform as expected.

These risks are fully discussed in the Portfolios’ prospectus. As with all investments, you may lose money by investing in the Portfolios.

An Important Note About Historical Performance

The investment return and principal value of an investment in the Portfolios will fluctuate, so that shares, when redeemed, may be worth more or less than their original cost. Performance shown in this report represents past performance and does not guarantee future results. Current performance may be lower or higher than the performance information shown. You may obtain performance information current to the most recent month-end by visiting www.abfunds.com. Class B shares are no longer being offered. Effective November 7, 2019, all outstanding Class B shares were converted to Class A shares. Please see Note A for more information.

All fees and expenses related to the operation of the Portfolios have been deducted. NAV returns do not reflect sales charges; if sales charges were reflected, the Portfolios’ quoted performance would be lower. SEC returns and the Portfolios’ returns shown in the line graphs reflect the applicable sales charges for each share class: a 3% maximum front-end sales charge for Class A shares and a 1% 1-year contingent deferred sales charge for Class C shares. Prior to October 1, 2009, the maximum front-end sales charge for Class A shares of the Portfolios was 4.25%. If the Class A annualized returns for the Portfolios and the National, California and New York Portfolio returns shown in the line graphs reflected the deduction of the former maximum front-end sales charge, their returns would be lower. Returns for the different share classes will vary due to their different expenses associated with each class. Performance assumes reinvestment of distributions and does not account for taxes.

HISTORICAL PERFORMANCE

AB CALIFORNIA PORTFOLIO

AVERAGE ANNUAL RETURNS AS OF NOVEMBER 30, 2020 (unaudited)

The Portfolio’s current prospectus fee table shows the Portfolio’s total annual operating expense ratios as 0.78%, 1.53% and 0.53% for Class A, Class C and Advisor Class shares, respectively, gross of any fee waivers or expense reimbursements. Contractual fee waivers and/or expense reimbursements will limit the Portfolio’s annual operating expenses, exclusive of any interest expense, to 0.75%, 1.50% and 0.50% for Class A, Class C and Advisor Class shares, respectively. These waivers/reimbursements may not be terminated prior to September 30, 2021 and may be extended by the Adviser for additional one-year terms. Absent reimbursements or waivers, performance would have been lower. The Financial Highlights section of this report sets forth expense ratio data for the current reporting period; the expense ratios shown above may differ from the expense ratios in the Financial Highlights section since they are based on different time periods.

HISTORICAL PERFORMANCE (continued)

AB CALIFORNIA PORTFOLIO

SEC AVERAGE ANNUAL RETURNS

AS OF THE MOST RECENT CALENDAR QUARTER-END

DECEMBER 31, 2020 (unaudited)

HISTORICAL PERFORMANCE

AB HIGH INCOME MUNICIPAL PORTFOLIO

AVERAGE ANNUAL RETURNS AS OF NOVEMBER 30, 2020 (unaudited)

The Portfolio’s current prospectus fee table shows the Portfolio’s total annual operating expense ratios as 0.85%, 1.60%, 0.60% and 0.59% for Class A, Class C, Advisor Class and Class Z shares, respectively, gross of any fee waivers or expense reimbursements. Contractual fee waivers and/or expense reimbursements will limit the Portfolio’s annual operating expenses, exclusive of any interest expense, to 0.80%, 1.55%, 0.55% and 0.54% for Class A, Class C, Advisor Class and Class Z shares, respectively. The Financial Highlights section of this report sets forth expense ratio data for the current reporting period; the expense ratios shown above may differ from the expense ratios in the Financial Highlights section since they are based on different time periods.

HISTORICAL PERFORMANCE (continued)

AB HIGH INCOME MUNICIPAL PORTFOLIO

SEC AVERAGE ANNUAL RETURNS

AS OF THE MOST RECENT CALENDAR QUARTER-END

DECEMBER 31, 2020 (unaudited)

HISTORICAL PERFORMANCE

AB NATIONAL PORTFOLIO

AVERAGE ANNUAL RETURNS AS OF NOVEMBER 30, 2020 (unaudited)

The Portfolio’s current prospectus fee table shows the Portfolio’s total annual operating expense ratios as 0.78%, 1.54% and 0.53% for Class A, Class C and Advisor Class shares, respectively, gross of any fee waivers or expense reimbursements. Contractual fee waivers and/or expense reimbursements will limit the Portfolio’s annual operating expenses to 0.75%, 1.50%, and 0.50% for Class A, Class C and Advisor Class shares, respectively. These waivers/reimbursements may not be terminated prior to September 30, 2021 and may be extended by the Adviser for additional one-year terms. Absent reimbursements or waivers, performance would have been lower. The Financial Highlights section of this report sets forth expense ratio data for the current reporting period; the expense ratios shown above may differ from the expense ratios in the Financial Highlights section since they are based on different time periods.

HISTORICAL PERFORMANCE (continued)

AB NATIONAL PORTFOLIO

SEC AVERAGE ANNUAL RETURNS

AS OF THE MOST RECENT CALENDAR QUARTER-END

DECEMBER 31, 2020 (unaudited)

HISTORICAL PERFORMANCE

AB NEW YORK PORTFOLIO

AVERAGE ANNUAL RETURNS AS OF NOVEMBER 30, 2020 (unaudited)

The Portfolio’s current prospectus fee table shows the Portfolio’s total annual operating expense ratios as 0.80%, 1.55% and 0.55% for Class A, Class C and Advisor Class shares, respectively, gross of any fee waivers or expense reimbursements. Contractual fee waivers and/or expense reimbursements will limit the Portfolio’s annual operating expenses, inclusive of interest expense, to 0.75%, 1.50% and 0.50% for Class A, Class C and Advisor Class shares, respectively. These waivers/reimbursements may not be terminated prior to September 30, 2021 and may be extended by the Adviser for additional one-year terms. Absent reimbursements or waivers, performance would have been lower. The Financial Highlights section of this report sets forth expense ratio data for the current reporting period; the expense ratios shown above may differ from the expense ratios in the Financial Highlights section since they are based on different time periods.

HISTORICAL PERFORMANCE (continued)

AB NEW YORK PORTFOLIO

SEC AVERAGE ANNUAL RETURNS

AS OF THE MOST RECENT CALENDAR QUARTER-END

DECEMBER 31, 2020 (unaudited)

EXPENSE EXAMPLE

(unaudited)

As a shareholder of a Portfolio, you incur two types of costs: (1) transaction costs, including sales charges (loads) on purchase payments, contingent deferred sales charges on redemptions and (2) ongoing costs, including management fees; distribution (12b-1) fees; and other Portfolio expenses. This example is intended to help you understand your ongoing costs (in dollars) of investing in the Portfolio and to compare these costs with the ongoing costs of investing in other mutual funds.

The Example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period as indicated below.

Actual Expenses

The first line of the table below provides information about actual account values and actual expenses. You may use the information in this line, together with the amount you invested, to estimate the expenses that you paid over the period. Simply divide your account value by $1,000 (for example, an $8,600 account value divided by $1,000 = 8.6), then multiply the result by the number in the first line under the heading entitled “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes

The second line of the table below provides information about hypothetical account values and hypothetical expenses based on a Portfolio’s actual expense ratio and an assumed annual rate of return of 5% before expenses, which is not the Portfolio’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Portfolio and other funds by comparing this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of other funds.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transactional costs, such as sales charges (loads), or contingent deferred sales charges on redemptions. Therefore, the second line of the table is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds. In addition, if these transactional costs were included, your costs would have been higher.

EXPENSE EXAMPLE (continued)

(unaudited)

AB California Portfolio

AB High Income Municipal Portfolio

AB National Portfolio

EXPENSE EXAMPLE (continued)

(unaudited)

AB New York Portfolio

BOND RATING SUMMARY¹

November 30, 2020 (unaudited)

BOND RATING SUMMARY¹ (continued)

November 30, 2020 (unaudited)

PORTFOLIO OF INVESTMENTS

AB CALIFORNIA PORTFOLIO

November 30, 2020 (unaudited)

PORTFOLIO OF INVESTMENTS (continued)

AB CALIFORNIA PORTFOLIO

PORTFOLIO OF INVESTMENTS (continued)

AB CALIFORNIA PORTFOLIO

PORTFOLIO OF INVESTMENTS (continued)

AB CALIFORNIA PORTFOLIO

PORTFOLIO OF INVESTMENTS (continued)

AB CALIFORNIA PORTFOLIO