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Pioneer Equity Income Fund

Class A Shares	Class C Shares	Class K Shares	Class R Shares	Class Y Shares
PEQIX	PCEQX	PEQKX	PQIRX	PYEQX

Summary Prospectus | March 1, 2022

Before you invest, you may want to review the fund’s prospectus, which contains more information about the fund and its risks. You can find the fund’s prospectus, statement of additional information and other information about the fund online at https://www.amundi.com/usinvestors/Resources/Download-Literature. You also can obtain this information at no cost by calling 1-800-225-6292 or by sending an email request to US.AskAmundiUS@amundi.com. The fund’s current prospectus and statement of additional information, dated March 1, 2022, and the independent registered public accounting firm’s report and financial statements in the fund’s annual report to shareholders dated October 31, 2021, are incorporated by reference into this summary prospectus.

Summary Prospectus

Investment objectives

Current income and long-term growth of capital from a portfolio consisting primarily of income producing equity securities of U.S. corporations.

Fees and expenses of the fund

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.

You may qualify for sales charge discounts if you or your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Pioneer funds. More information about these and other discounts is available from your investment professional and in the “Sales charges” section of the prospectus beginning on page 43, the “Intermediary defined sales charge waiver policies” section of the prospectus beginning on page 81, and the “Sales charges” section of the statement of additional information beginning on page 50. If you invest in Class K shares or Class Y shares through an investment professional or financial intermediary, that investment professional or financial intermediary may charge you a commission. Such commissions, if any, are not charged by the fund and are not reflected in the fee table or expense example below.

Shareowner fees

(fees paid directly from your investment)

	Class A	Class C	Class K	Class R	Class Y
Maximum sales charge (load) when you buy shares (as a percentage of offering price)	5.75%	None	None	None	None
Maximum deferred sales charge (load) (as a percentage of offering price or the amount you receive when you sell shares, whichever is less)	None1	1%	None	None	None

Annual fund operating expenses

(expenses that you pay each year as a percentage of the value of your investment)

	Class A	Class C	Class K	Class R	Class Y
Management Fees	0.60%	0.60%	0.60%	0.60%	0.60%
Distribution and Service (12b-1) Fees	0.25%	1.00%	0.00%	0.50%	0.00%
Other Expenses	0.17%	0.15%	0.06%	0.27%	0.18%
Total Annual Fund Operating Expenses	1.02%	1.75%	0.66%	1.37%	0.78%

Class A purchases of $500,000 or more that are not subject to an initial sales charge may be subject to a contingent deferred sales charge of 1%. See “Sales charges.”

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the fund for the time periods shown and then, except as indicated, redeem all of your shares at the end of those periods. It also assumes that (a) your investment has a 5% return each year and (b) the fund's total annual operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	If you redeem your shares				If you do not redeem your shares
	Number of years you own your shares
	1	3	5	10	1	3	5	10
Class A	$673	$881	$1,106	$1,751	$673	$881	$1,106	$1,751
Class C	278	551	949	2,062	178	551	949	2,062
Class K	67	211	368	822	67	211	368	822
Class R	139	434	750	1,646	139	434	750	1,646
Class Y	80	249	433	966	80	249	433	966

Portfolio turnover

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 25% of the average value of its portfolio.

Principal investment strategies

Normally, the fund invests at least 80% of its total assets in income producing equity securities of U.S. issuers. The income producing equity securities in which the fund may invest include common stocks, preferred stocks, funds that invest primarily in equity securities and equity interests in real estate investment trusts (REITs). The remainder of the fund may be invested in debt securities, most of which are expected to be convertible into common stocks. The fund may invest in initial public offerings of equity securities.

The fund may invest up to 20% of its total assets in securities of non-U.S. issuers, including depositary receipts. The fund will not invest more than 5% of its total assets in the securities of emerging markets issuers.

The fund may invest up to 20% of its net assets in REITs.

Summary Prospectus

The fund also may invest in investment grade and below investment grade debt securities (known as “junk bonds”). The fund may invest up to 10% of its net assets in junk bonds, including below investment grade convertible debt securities.

The fund may, but is not required to, use derivatives, such as stock index futures and options. The fund may use derivatives for a variety of purposes, including: in an attempt to hedge against adverse changes in the market price of securities, interest rates or currency exchange rates; as a substitute for purchasing or selling securities; to attempt to increase the fund's return as a non-hedging strategy that may be considered speculative; to manage portfolio characteristics; and as a cash flow management technique. The fund may choose not to make use of derivatives for a variety of reasons, and any use may be limited by applicable law and regulations. The fund may also hold cash or other short-term investments.

The fund's investment adviser uses a value approach to select the fund's investments to buy and sell. The adviser seeks securities that are selling at substantial discounts to their underlying values and then holds these securities until the market values reflect their intrinsic values. The adviser evaluates a security’s potential value, including the attractiveness of its market valuation, based on the company’s assets and prospects for earnings growth. The adviser also considers a security’s potential to provide a reasonable amount of income. In making these assessments, the adviser employs fundamental research and an evaluation of the issuer based on its financial statements and operations, employing a bottom-up analytic style, which focuses on specific securities rather than on industries. The adviser generally sells a portfolio security when it believes that the security’s market value reflects its underlying value.

The adviser integrates environmental, social and corporate governance (ESG) considerations into its investment research process by evaluating the business models and practices of issuers and their ESG-related risks. The adviser believes ESG analysis is a meaningful facet of fundamental research, the process of evaluating an issuer based on its financial position, business operations, competitive standing and management. This process considers ESG information, where available, in assessing an investment’s performance potential. The adviser generally considers ESG information in the context of an issuer’s respective sector or industry. The adviser may consider ESG ratings provided by third parties or internal sources, as well as issuer disclosures and public information, in evaluating issuers. ESG considerations are not a primary focus of the fund, and the weight given by the adviser to ESG considerations in making investment decisions will vary and, for any specific decision, they may be given little or no weight.

Principal risks of investing in the fund

You could lose money on your investment in the fund. As with any mutual fund, there is no guarantee that the fund will achieve its objectives.

Market risk. The market prices of securities or other assets held by the fund may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions, recessions, inflation, changes in interest or currency rates, lack of liquidity in the bond markets, the spread of infectious illness or other public health issues, market disruptions caused by tariffs, trade disputes or other factors or adverse investor sentiment. If the market prices of the fund's securities and assets fall, the value of your investment will go down. A change in financial condition or other event affecting a single issuer may adversely impact securities markets as a whole. The value of assets or income from investment may be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the fund’s assets can decline as can the value of the fund’s distributions.

In the past decade, financial markets throughout the world have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. Governmental and non-governmental issuers have defaulted on, or been forced to restructure, their debts. These conditions may continue, recur, worsen or spread. Events that have contributed to these market conditions include, but are not limited to, major cybersecurity events; geopolitical events (including wars and terror attacks); measures to address budget deficits; downgrading of sovereign debt; changes in oil and commodity prices; changes in currency exchange rates; global pandemics; and public sentiment. U.S. and non-U.S. governments and central banks have provided significant support to financial markets, including by keeping interest rates at historically low levels. U.S. Federal Reserve or other U.S. or non-U.S. governmental or central bank actions, including interest rate increases or decreases, or contrary actions by different governments, could negatively affect financial markets generally, increase market volatility and reduce the value and liquidity of securities in which the fund invests. Policy and legislative changes in the U.S. and in other countries are affecting many aspects of financial regulation, and these and other events affecting global markets, such as the United Kingdom’s exit from the European Union (or Brexit) or potential trade imbalances with China, or other countries may in some instances contribute to decreased liquidity and increased volatility in the financial markets. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time.

Summary Prospectus

Economies and financial markets throughout the world are increasingly interconnected. Economic, financial or political events, trading and tariff arrangements, armed conflict, terrorism, natural disasters, infectious illness or public health issues, cybersecurity events, supply chain disruptions, and other circumstances in one country or region could have profound impacts on global economies or markets. As a result, whether or not the fund invests in securities of issuers located in or with significant exposure to the countries directly affected, the value and liquidity of the fund’s investments may be negatively affected. The fund may experience a substantial or complete loss on any individual security or derivative position.

The global pandemic of the novel coronavirus respiratory disease designated COVID-19 has resulted in major disruption to economies and markets around the world, including the United States. Global financial markets have experienced extreme volatility and severe losses, and trading in many instruments has been disrupted. Liquidity for many instruments has been greatly reduced for periods of time. Some interest rates are very low and in some cases yields are negative. Some sectors of the economy and individual issuers have experienced particularly large losses. Rates of inflation have recently risen. These circumstances may continue for an extended period of time, and may continue to affect adversely the value and liquidity of the fund’s investments. Governments and central banks, including the Federal Reserve in the U.S., have taken extraordinary and unprecedented actions to support local and global economies and the financial markets. These actions have resulted in significant expansion of public debt, including in the U.S. The impact of these measures may not be known for some time. The consequences of high public debt, including its future impact on the economy and securities markets, likewise may not be known for some time.

Value style risk. The prices of securities the adviser believes are undervalued may not appreciate as expected or may go down. Value stocks may fall out of favor with investors and underperform the overall equity market.

Income producing securities risk. Income producing securities may fall out of favor with investors and underperform the overall equity market.

Large capitalization companies risk. Large capitalization companies may fall out of favor with investors and underperform the overall equity market.

Portfolio selection risk. The adviser's judgment about a particular security or issuer, or about the economy or a particular sector, region or market segment, or about an investment strategy, may prove to be incorrect, or there may be imperfections, errors or limitations in the models, tools and data used by the adviser.

ESG risk. The fund’s adviser considers ESG information in its investment research process. This may mean forgoing some investment opportunities available to funds that do not consider ESG information. To the extent the adviser considers this information, the adviser focuses on investment considerations that relate to potential return and risk, without sacrificing these considerations for non-economic purposes. In considering ESG information, the adviser may use third party ESG ratings information that it believes to be reliable, but such information may not be accurate or complete, or may be biased. ESG considerations are not a primary focus of the fund, and the weight given by the adviser to ESG considerations in making investment decisions will vary and, for any specific decision, they may be given little or no weight.

Risks of non-U.S. investments. Investing in non-U.S. issuers, or in U.S. issuers that have significant exposure to foreign markets, may involve unique risks compared to investing in securities of U.S. issuers. These risks are more pronounced for issuers in emerging markets or to the extent that the fund invests significantly in one region or country. These risks may include different financial reporting practices and regulatory standards, less liquid trading markets, extreme price volatility, currency risks, changes in economic, political, regulatory and social conditions, terrorism, sustained economic downturns, financial instability, reduction of government or central bank support, inadequate accounting standards, tariffs, tax disputes or other tax burdens, and investment and repatriation restrictions. Lack of information and less market regulation also may affect the value of these securities. Withholding and other non-U.S. taxes may decrease the fund’s return. Non-U.S. issuers may be located in parts of the world that have historically been prone to natural disasters. Emerging market economies tend to be less diversified than those of more developed countries. They typically have fewer medical and economic resources than more developed countries and thus they may be less able to control or mitigate the effects of a pandemic. Investing in depositary receipts is subject to many of the same risks as investing directly in non-U.S. issuers. Depositary receipts may involve higher expenses and may trade at a discount (or premium) to the underlying security. A number of countries in the European Union (EU) have experienced, and may continue to experience, severe economic and financial difficulties. In addition, the United Kingdom has withdrawn from the EU (commonly known as “Brexit”). The range and potential implications of possible political, regulatory, economic, and market outcomes of Brexit cannot be fully known but could be significant, potentially resulting in increased volatility, illiquidity and potentially lower economic growth in the affected markets, which will adversely affect the fund's investments. Sanctions or other government actions against a foreign nation could negatively impact the fund’s investments in securities that

Summary Prospectus

have exposure to that nation. The Ukraine has experienced ongoing military conflict; this conflict may expand and military conflicts could potentially occur elsewhere in Europe. China and other developing market Asia-Pacific countries may be subject to considerable degrees of economic, political and social instability. In addition, the U.S. government has imposed restrictions on U.S. investor participation in certain Chinese investments. These matters could adversely affect China’s economy.

Risks of investments in real estate related securities. Investments in real estate securities are affected by economic conditions, interest rates, governmental actions and other factors. In addition, investing in REITs involves unique risks. They are significantly affected by the market for real estate and are dependent upon management skills and cash flow. REITs may have lower trading volumes and may be subject to more abrupt or erratic price movements than the overall securities markets. Mortgage REITs are particularly subject to interest rate and credit risks. In addition to its own expenses, the fund will indirectly bear its proportionate share of any management and other expenses paid by REITs in which it invests. Many real estate companies, including REITs, utilize leverage.

Risks of initial public offerings. Companies involved in initial public offerings (IPOs) generally have limited operating histories, and prospects for future profitability are uncertain. The market for IPO issuers has been volatile, and share prices of newly public companies have fluctuated significantly over short periods of time. The purchase of IPO shares may involve high transaction costs.

Risks of investment in other funds. Investing in other investment companies, including exchange-traded funds (ETFs) and closed-end funds, subjects the fund to the risks of investing in the underlying securities or assets held by those funds. When investing in another fund, the fund will bear a pro rata portion of the underlying fund’s expenses, including management fees, in addition to its own expenses. ETFs and closed-end funds are bought and sold based on market prices and can trade at a premium or a discount to the ETF’s or closed-end fund’s net asset value.

Risks of convertible securities. The market values of convertible securities tend to decline as interest rates increase and, conversely, to increase as interest rates decline. A downturn in equity markets may cause the price of convertible securities to decrease relative to other fixed income securities.

Preferred stocks risk. Preferred stocks may pay fixed or adjustable rates of return. Preferred stocks are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred stocks generally pay dividends only after the company makes required payments to holders of its

bonds and other debt. Thus, the value of preferred stocks will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. The market value of preferred stocks generally decreases when interest rates rise. Preferred stocks of smaller companies may be more vulnerable to adverse developments than preferred stocks of larger companies.

Debt securities risk. Factors that could contribute to a decline in the market value of debt securities in the fund include rising interest rates, if the issuer or other obligor of a security held by the fund fails to pay principal and/or interest, otherwise defaults or has its credit rating downgraded or is perceived to be less creditworthy or the credit quality or value of any underlying assets declines. A general rise in interest rates could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions from the fund. Junk bonds have a higher risk of default or are already in default and are considered speculative.

High yield or “junk” bond risk. Debt securities that are below investment grade, called “junk bonds,” are speculative, have a higher risk of default or are already in default, tend to be less liquid and are more difficult to value than higher grade securities. Junk bonds tend to be volatile and more susceptible to adverse events and negative sentiments. These risks are more pronounced for securities that are already in default.

Market segment risk. To the extent the fund emphasizes, from time to time, investments in a market segment, the fund will be subject to a greater degree to the risks particular to that segment, and may experience greater market fluctuation than a fund without the same focus.

Industries in the financial segment, such as banks, insurance companies, broker-dealers and real estate investment trusts (REITs), may be sensitive to changes in interest rates and general economic activity and are generally subject to extensive government regulation.

Derivatives risk. Using stock index futures and options and other derivatives can increase fund losses and reduce opportunities for gains when market prices, interest rates, currencies or the derivative instruments themselves behave in a way not anticipated by the fund. Using derivatives may increase the volatility of the fund's net asset value and may not provide the result intended. Derivatives may have a leveraging effect on the fund. Some derivatives have the potential for unlimited loss, regardless of the size of the fund’s initial investment. Derivatives are generally subject to the risks applicable to the assets, rates, indices or other indicators underlying the derivative. Changes in a derivative’s value may not correlate well with the

Summary Prospectus

referenced asset or metric. The fund also may have to sell assets at inopportune times to satisfy its obligations. Derivatives may be difficult to sell, unwind or value, and the counterparty may default on its obligations to the fund. Use of derivatives may have different tax consequences for the fund than an investment in the underlying security, and such differences may affect the amount, timing and character of income distributed to shareholders. The U.S. government and foreign governments are in the process of adopting and implementing regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make them more costly, limit their availability or utility, otherwise adversely affect their performance or disrupt markets.

Leveraging risk. The value of your investment may be more volatile and other risks tend to be compounded if the fund borrows or uses derivatives or other investments, such as ETFs, that have embedded leverage. Leverage generally magnifies the effect of any increase or decrease in the value of the fund's underlying assets and creates a risk of loss of value on a larger pool of assets than the fund would otherwise have, potentially resulting in the loss of all assets. Engaging in such transactions may cause the fund to liquidate positions when it may not be advantageous to do so to satisfy its obligations or meet segregation requirements.

Valuation risk. The sales price the fund could receive for any particular portfolio investment may differ from the fund’s valuation of the investment, particularly for illiquid securities and securities that trade in thin or volatile markets or that are valued using a fair value methodology. These differences may increase significantly and affect fund investments more broadly during periods of market volatility. Investors who purchase or redeem fund shares on days when the fund is holding fair-valued securities may receive fewer or more shares or lower or higher redemption proceeds than they would have received if the fund had not fair-valued the securities or had used a different valuation methodology. The fund’s ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third party service providers.

Liquidity risk. Some securities and derivatives held by the fund may be or become impossible or difficult to purchase, sell or unwind, particularly during times of market turmoil. Illiquid securities and derivatives also may be difficult to value. If the fund is forced to sell an illiquid asset or unwind a derivatives position to meet redemption requests or other cash needs, the fund may be forced to sell at a loss.

Redemption risk. The fund may experience heavy redemptions that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value, which could cause the value of your investment to decline.

Cybersecurity risk. Cybersecurity failures by and breaches of the fund’s adviser, transfer agent, distributor, custodian, fund accounting agent or other service providers may disrupt fund operations, interfere with the fund’s ability to calculate its NAV, prevent fund shareholders from purchasing, redeeming or exchanging shares or receiving distributions, cause loss of or unauthorized access to private shareholder information, and result in financial losses to the fund and its shareholders, regulatory fines, penalties, reputational damage, or additional compliance costs.

Expense risk. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if overall net assets decrease. Net assets are more likely to decrease and fund expense ratios are more likely to increase when markets are volatile.

Please note that there are many other factors that could adversely affect your investment and that could prevent the fund from achieving its goals.

An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

The fund's past performance

The bar chart and table indicate the risks and volatility of an investment in the fund by showing how the fund has performed in the past. The bar chart shows changes in the performance of the fund's Class A shares from calendar year to calendar year. The table shows the average annual total returns for each class of the fund over time and compares these returns to the returns of the Russell 1000 Value Index, a broad-based measure of market performance that has characteristics relevant to the fund’s investment strategies.
You can obtain updated performance information by visiting https://www.amundi.com/usinvestors/Products/Mutual-Funds or by calling 1-800-225-6292.

The fund's past performance (before and after taxes) does not necessarily indicate how it will perform in the future.

The bar chart does not reflect any sales charge you may pay when you buy fund shares. If this amount was reflected, returns would be less than those shown.

Summary Prospectus

Annual return Class A shares (%)

(Year ended December 31)

For the period covered by the bar chart:

	Returns	Period Beginning	Period Ending
Highest Calendar Quarter	15.53%	04/01/2020 to	06/30/2020
Lowest Calendar Quarter	-26.51%	01/01/2020 to	03/31/2020

Average annual total return (%)

(for periods ended December 31, 2021)

	1 Year	5 Years	10 Years	Since Inception	Inception Date
Class A					7/25/90
Return before taxes	18.32	9.18	11.46	9.70
Return after taxes on distributions	15.74	7.76	9.67	8.21
Return after taxes on distributions and sale of shares	12.47	7.00	8.98	7.89
Class C†	23.65	9.68	11.31	8.04	1/31/96
Class K	25.99	10.89	N/A	12.62	12/20/12
Class R	25.12	10.06	11.72	9.79	4/1/03
Class Y	25.83	10.76	12.43	7.86	7/2/98
Russell 1000 Value Index (reflects no deduction for fees, expenses or taxes)	25.16	11.16	12.97	10.26	7/25/90

†

The performance of Class C shares does not reflect the 1% front-end sales charge in effect prior to February 1, 2004. If you paid a 1% sales charge, your returns would be lower than those shown above.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor's tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

After-tax returns are shown only for Class A shares. After-tax returns for Class C, Class K, Class R and Class Y shares will vary.

Management

Investment adviser	Amundi Asset Management US, Inc. (“Amundi US”)
Portfolio management	John A. Carey, Managing Director, Director of Equity Income, U.S. of Amundi US (lead portfolio manager of the fund since 1990); Walter Hunnewell, Jr., Vice President of Amundi US (portfolio manager of the fund since 2001); and Sammi Truong, Vice President of Amundi US (portfolio manager of the fund since 2018)

Purchase and sale of fund shares

You may purchase, exchange or sell (redeem) shares each day the New York Stock Exchange is open through your financial intermediary or, for accounts held directly with the fund, by contacting the fund in writing or by telephone: Pioneer Funds, P.O. Box 9897, Providence, RI 02940-8097, tel. 1-800-225-6292.

Your initial investment for Class A or Class C shares must be at least $1,000. Additional investments must be at least $100 for Class A shares and $500 for Class C shares. Generally, the initial investment for Class K or Class Y shares must be at least $5 million. This amount may be invested in one or more of the Pioneer mutual funds that currently offer Class K or Class Y shares, as applicable. There is no minimum additional investment amount for Class K or Class Y shares. There is no minimum investment amount for Class R shares.

Tax information

The fund intends to make distributions that may be taxed as ordinary income, qualified dividend income, or capital gains.