Pioneer High Yield Fund NCSR Certified annual shareholder report (management investment company)

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- 09685

Pioneer High Yield Fund

(Exact name of registrant as specified in charter)

60 State Street, Boston, MA 02109

(Address of principal executive offices) (ZIP code)

Terrence J. Cullen, Amundi Pioneer Asset Management, Inc.,

60 State Street, Boston, MA 02109

(Name and address of agent for service)

Registrant’s telephone number, including area code: (617) 742-7825

Date of fiscal year end: October 31, 2020

Date of reporting period: November 1, 2019 through October 31, 2020

Form N-CSR is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule 30e-1 under the Investment Company Act of 1940 (17 CFR 270.30e-1). The Commission may use the information provided on Form N-CSR in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-CSR, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-CSR unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. ss. 3507.

Pioneer High
Yield Fund

Annual Report | October 31, 2020


A: TAHYX	C: PYICX	R: TYHRX	Y: TYHYX

Beginning in or after April 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s shareholder reports like this one will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or from your financial intermediary, such as a broker-dealer, bank or insurance company. Instead, the reports will be made available on the Fund’s website, and you will be notified by mail each time a report is posted and provided with a website link 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 electronically by contacting your financial intermediary or, if you invest directly with the Fund, by calling 1-800-225-6292.

You may elect to receive all future reports in paper free of charge. If you invest directly with the Fund, you can inform the Fund that you wish to continue receiving paper copies of your shareholder reports by calling 1-800-225-6292. 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. Your election to receive reports in paper will apply to all funds held in your account if you invest through your financial intermediary or all funds held within the Pioneer Fund complex if you invest directly.

visit us: www.amundipioneer.com/us

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President’s Letter

Dear Shareholders,

The new decade has arrived delivering a calendar year that will go down in the history books. The beginning of 2020 seemed to extend the positive market environment of 2019. Then, March roared in like a lion and the COVID-19 pandemic became a global crisis impacting lives and life as we know it. As the fourth quarter of 2020 got underway, it appeared that the long-anticipated “second wave” of COVID-19 cases was occurring, both in some U.S. states and in Europe. In response, some governments began retightening restrictions on both business and personal activities.

However, as the fourth quarter continued, we began to read some encouraging news on the vaccine front, as multiple pharmaceutical companies announced successful clinical trials for their COVID-19 vaccinations and applied for emergency-use approval for the drugs with the Food and Drug Administration. Government officials followed up on the positive news by announcing that deployment of at least one of the vaccines to frontline workers could begin even before the end of this calendar year, with the potential for widespread distribution by mid-2021.

While there may finally be a light visible at the end of the pandemic tunnel as 2020 comes to a close, the long-term impact on the global economy from COVID-19, while currently unknown, is likely to be considerable. It is clear that several industries have already felt greater effects than others, and the markets, which do not thrive on uncertainty, have been volatile, delivering significantly negative performance in the first quarter, and then recovering most of those losses throughout the following quarters. Despite the rebound, volatility has remained elevated, with momentum rising and falling on seemingly every bit of positive or negative news about the virus, from vaccines to spikes in the number of cases as well as rising hospitalization rates in some areas. In addition, the U.S. Presidential Election was in high gear as we entered the fourth quarter. This election contributed to the market volatility as investors pondered the possible outcomes and their potential effects on the economic outlook.

With the advent of COVID-19 last winter, we implemented our business continuity plan according to the new COVID-19 guidelines, and most of our employees have been working remotely since March. To date, our operating environment has faced no interruption. I am proud of the careful planning that has taken place and confident we can maintain this environment for as long as is prudent. History in the making for a company that first opened its doors way back in 1928.

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Since 1928, Amundi’s investment process has been built on a foundation of fundamental research and active management, principles which have guided our investment decisions for more than 90 years. We believe active management – that is, making active investment decisions – can help mitigate the risks during periods of market volatility. As 2020 has reminded us, investment risk can arise from a number of factors in today’s global economy, including slower or stagnating growth, changing U.S. Federal Reserve policy, oil price shocks, political and geopolitical factors and, unfortunately, major public health concerns such as a viral pandemic.

At Amundi, active management begins with our own fundamental, bottom-up research process. Our team of dedicated research analysts and portfolio managers analyzes each security under consideration, communicating directly with the management teams of the companies issuing the securities and working together to identify those securities that best meet our investment criteria for our family of funds. Our risk management approach begins with each and every security, as we strive to carefully understand the potential opportunity, while considering any and all risk factors.

Today, as investors, we have many options. It is our view that active management can serve shareholders well, not only when markets are thriving, but also during periods of market stress.

As you consider your long-term investment goals, we encourage you to work with your financial professional to develop an investment plan that paves the way for you to pursue both your short-term and long-term goals.

We remain confident that the current crisis, like others in human history, will pass, and we greatly appreciate the trust you have placed in us and look forward to continuing to serve you in the future.

Sincerely,

Lisa M. Jones
Head of the Americas, President and CEO of U.S.
Amundi Pioneer Asset Management USA, Inc.
December 18, 2020

Any information in this shareowner report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results.

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Portfolio Management Discussion | 10/31/20

In the following interview, portfolio managers Andrew Feltus and Matthew Shulkin discuss the factors that influenced Pioneer High Yield Fund’s performance for the 12-month period ended October 31, 2020. Mr. Feltus, Managing Director, Co-Director of High Yield, and a portfolio manager at Amundi Pioneer Asset Management, Inc. (Amundi)*, Mr. Shulkin, a senior vice president and a portfolio manager at Amundi, and Kenneth Monaghan, Co-Director of High Yield and a portfolio manager at Amundi, are responsible for the daily management of the Fund.

Q How did the Fund perform during the 12-month period ended October 31, 2020?

A Pioneer High Yield Fund’s Class A shares returned -0.89% at net asset value during the 12-month period ended October 31, 2020, while the Fund’s benchmarks, the ICE Bank of America (ICE BofA) U.S. High Yield Index (the high-yield index) and the ICE BofA All-Convertibles Speculative Quality Index, returned 2.54% and 61.05%, respectively.

During the same period, the average return of the 677 mutual funds in Morningstar’s High Yield Bond Funds category was 1.43%.

Q Could you please describe the market environment for high-yield investors during the 12-month period ended October 31, 2020?

A Entering the period in November of 2019, positive market sentiment prevailed, supported by an accommodative Federal Reserve (Fed), which had cut the target range of its benchmark overnight lending rate by a quarter-point at three successive meetings earlier in 2019. The investment backdrop for riskier assets received a further boost from news in December that the U.S. and China had moved towards a “phase one” trade deal, which the parties formally signed in January of 2020.

However, beginning in mid-February of 2020, performance in the financial markets began to deteriorate, driven by the effects of the COVID-19 virus, which originated in China, but quickly became a global pandemic. Economies around the world ground to a near halt during March, as public health concerns led to the rapid implementation by governments and businesses of extreme lockdown measures focused on virus containment. In addition, oil prices plummeted to 20-year lows, responding to slumping global demand resulting from the spread of COVID-19, as well as a supply shock spurred by a price war between Saudi Arabia and Russia.

* See Notes to Financial Statements Note 9.

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In the financial markets, uncertainty over the scope and duration of the pandemic crisis as well as investors’ need for cash drove wholesale liquidations across most asset classes and a flight-to-safety trade that drove U.S. Treasury yields to historic lows. Significant selling in U.S. dollar (USD) fixed-income markets eventually stressed market functionality and led to price dislocations in all segments, even Treasury bonds. Performance of U.S. high-yield bonds declined sharply, as the outlook shifted from growth to recession, and investors anticipated the high-yield default rate moving well into double digits.

The unprecedented shutting down of much of the economy due to COVID-19 spurred extraordinary monetary and fiscal policy responses. The Fed jumped into action by dusting off its 2008/2009 policy “playbook” and rapidly rolling out a raft of programs aimed at restoring market liquidity, facilitating credit availability, and bolstering investors’ confidence. The measures included reducing the benchmark federal funds rate target range to near zero and committing to a broad range of fixed-income asset purchases. The Fed also entered uncharted waters with the announcement on March 23 of purchasing programs in support of corporate bonds in both the new-issue and secondary markets. On the fiscal side, Congress and the White House agreed upon a $2.2 trillion stimulus bill at the end of March, and then provided further support a few weeks later with another package worth nearly $500 billion, including aid to small businesses.

The result of the unprecedented scope and speed of the responses from policymakers was a rebound in the markets for riskier assets, including high-yield corporates, over the second quarter of 2020, and a subsequent stabilization in valuations. Over the last few months of the 12-month period, uncertainties over the November U.S. election and the continued spread of COVID-19 affected the markets, but reassurances from the Fed that interest-rate policy would remain accommodative, and progress towards a possible vaccine for the virus, offset those concerns and caused credit spreads within the high-yield market to grind tighter. (Credit spreads are commonly defined as the differences in yield between Treasuries and other types of fixed-income securities with similar maturities.)

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Q Can you review the Fund’s principal strategies during the 12-month period ended October 31, 2020, and the degree to which they added to or detracted from returns versus the benchmark?

A In broad terms, at the beginning of the period, we had positioned the Fund to potentially benefit from continued consumer strength, given generally sound household balance sheets and a backdrop of nearly full employment and rising wages. In terms of individual sectors, we had overweighted the portfolio to airline, gaming, and leisure credits. In addition, we had continued to avoid investing in retail credits, for the most part, given the secular challenges facing the sector. That positioning worked out well for the Fund early in the 12-month period, but ultimately detracted from relative performance as the economy, and specifically those consumer-focused sectors, effectively closed down at the outset of the COVID-19 crisis. In addition, a modest Fund overweight to energy issues had a negative effect on relative returns as the sector struggled more than the rest of the high-yield market, given the severe weakness in oil prices for most of the 12-month period. The portfolio’s up-in-quality bias and strong individual security selection results within the sector helped to offset some of the negatives deriving from Fund’s slight overweight.

In terms of overall credit quality, the Fund’s underweight compared to the benchmark to higher-quality issues in the “BB” ratings range of the high-yield market acted as a further constraint on relative performance, as that market segment held up better over the full 12-month period as compared with other credit tiers.

Leading individual positive contributors to the Fund’s relative performance for the 12-month period included lack of portfolio exposure to the debt of Valaris, and positions in Exact Sciences and The Medicines Company. Valaris, along with other offshore drillers, performed poorly during the 12-month period as the decline in oil prices led to lower “day rates,” or equipment rental rates, and the company ultimately filed for bankruptcy in August. The Fund’s positions in the strong-performing convertible bonds of Exact Sciences, the producer of the “Cologuard” colon cancer home-detection test, and The Medicines Company, an anticoagulant producer acquired by a competitor early this year, also benefited benchmark-relative results. The Fund’s overweight position in

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wireless company Sprint also contributed strongly to relative returns, as T-Mobile’s acquisition of Sprint closed early in 2020. (T-Mobile is not a Fund holding.)

Leading individual detractors from the Fund’s benchmark-relative performance during the 12-month period included positions in the debt of Baytex, a Canadian exploration & production company with operations in both the U.S. and Canada; Shelf Drilling, an international operator of jack-up drilling rigs; and PBF Energy, one of the largest independent refinery operators in the U.S. As energy was the weakest sector within high yield during the 12-month period, the worst performers within energy tended to be companies with either high costs or high levels of leverage. A position in American Airlines was among the biggest non-energy performance laggards in the portfolio, as was Diamond Sports, a regional sports network that struggled as COVID-19 forced the cancellation of live sporting events for several months during the spring and summer.

Q Can you discuss the factors that affected the Fund’s income-generation, or distributions** to shareholders, either positively or negatively, during the 12-month period ended October 31, 2020?

A The Fund’s income-generation and distributions provided to shareholders remained relatively stable over the 12-month period. The portfolio’s positions in convertible securities and bank loans can at times result in a lower yield compared to the yield of a portfolio composed entirely of high-yield bonds. However, we view those allocations as beneficial to the Fund’s total-return profile, and we have been able to construct the portfolio’s holdings in a way that has typically allowed it to provide an average yield near that of the benchmark.

Q Did the Fund have any exposure to derivatives during the 12-month period ended October 31, 2020? If so, did the use of derivatives have an effect on the Fund’s performance?

A We invested the portfolio in index-based credit default swaps in an effort to maintain the desired level of exposure to the high-yield market, while also seeking to maintain sufficient liquidity that would allow us to make opportunistic purchases, and to help meet any unanticipated redemption requests. The strategy had a neutral impact on the Fund’s performance during the 12-month period.

** Distributions are not guaranteed.

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Q What is your assessment of the current climate for high-yield investing?

A Domestic economic activity rebounded by an estimated 38% (annualized) during the third quarter, recovering more than 75% of the output drawdown recorded during the first half of 2020. While the U.S. economic growth rate is likely to slow from that pace in the fourth quarter, we believe economic activity could continue to expand. History has typically shown that expansions have tended to be self-sustaining, unless derailed by an exogenous shock. While another injection of fiscal stimulus from the government could accelerate economic activity, we anticipate that growth may continue even without additional help, as personal savings balances have remained above historical norms. Although a continued increase in COVID-19 infections seems likely to occur during the winter months, we do not expect that sustained, widespread lockdowns will be necessary, given improved treatment methods.

We appreciate the near-term risks arising from U.S. political uncertainty, particularly with control of the U.S. Senate still to be determined in Georgia's run-off elections in January; a seasonal increase in COVID-19 infections; and an unexpected delay in the approval and deployment of a vaccine (or vaccines) for the virus. At the same time, we have framed those risks against asset-class spreads that, as of period-end, had generally resided above the levels seen at the beginning of 2020, which we believe leaves room for future spread tightening. In addition, we believe the medium-term fundamental outlook has remained positive, given continued improvement in COVID-19 treatments, the possibility for vaccine approvals sooner than originally expected, and accommodative financial conditions that seem unlikely to be reversed by tighter monetary policy from the Fed, which has pledged to keep the federal funds target range at near zero for the foreseeable future.

With high-yield corporate spreads above their long-term average, we believe investors have been receiving fair compensation for taking on added credit risk. While default rates could remain elevated over the near term, any improvement as we enter 2021 could support further spread tightening. Historically, spread tightening has begun well before the default rate has peaked. In the meantime, we believe the below-investment-grade market may continue to benefit from investors’ search for better yields.

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In response to the new economic environment, we have categorized all of the Fund’s holdings based on their relative exposure to the COVID-19 crisis. Sectors we view as “unimpaired” are those that have experienced minimal negative effects from the crisis, such as food and drug retailers. The “wounded” category includes companies that have experienced temporary disruptions due to COVID-19, but that we believe have good long-term business models, such as ambulatory surgery centers. In the “impaired” category are sectors where we expect to see lasting negative effects caused by the pandemic, such as movie theaters. We have found most unimpaired bonds to be expensive, and so we are interested in purchasing the debt of only the strongest issuers within the impaired sectors noted above.

We believe the Fund has the potential to generate the most alpha (incremental performance) within the wounded sectors, where diligent research could help us to identify the potential “survivors” once the COVID-19 situation has largely abated, whenever that may occur.

Please refer to the Schedule of Investments on pages 19–39 for a full listing of Fund securities.

All investments are subject to risk, including the possible loss of principal. In the past several years, financial markets have experienced increased volatility and heightened uncertainty. The market prices of securities 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 or adverse investor sentiment. These conditions may continue, recur, worsen or spread.

Investments in high-yield or lower-rated securities are subject to greater-than-average price volatility, illiquidity and possibility of default.

When interest rates rise, the prices of fixed-income securities held by the Fund will generally fall. Conversely, when interest rates fall, the prices of fixed-income securities held by the Fund will generally rise.

Investments in the Fund are subject to possible loss due to the financial failure of issuers of underlying securities and their inability to meet their debt obligations.

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Prepayment risk is the chance that an issuer may exercise its right to prepay its security, if falling interest rates prompt the issuer to do so. Forced to reinvest the unanticipated proceeds at lower interest rates, the Fund would experience a decline in income and lose the opportunity for additional price appreciation.

The Fund may invest in mortgage-backed securities, which during times of fluctuating interest rates may increase or decrease more than other fixed-income securities. Mortgage-backed securities are also subject to prepayments.

The Fund may use derivatives, such as options, futures, inverse floating rate obligations, swaps, and others, which can be illiquid, may disproportionately increase losses, and have a potentially large impact on Fund performance. Derivatives may have a leveraging effect on the Fund.

These risks may increase share price volatility.

Before investing, consider the product’s investment objectives, risks, charges and expenses. Contact your advisor or Amundi for a prospectus or summary prospectus containing this information. Read it carefully.

Any information in this shareholder report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results.

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Portfolio Summary | 10/31/20

10 Largest Holdings

(As a percentage of total investments)*


1.	U.S. Treasury Bills, 11/17/20	3.71%
2.	U.S. Treasury Floating Rate Notes, 0.4% (3 Month U.S. Treasury Bill Money
	Market Yield + 30 bps), 10/31/21	1.52
3.	Garda World Security Corp., 9.5%, 11/1/27 (144A)	1.08
4.	Iron Mountain, Inc., 4.875%, 9/15/27 (144A)	1.03
5.	Level 3 Financing, Inc., 4.625%, 9/15/27 (144A)	1.01
6.	KB Home, 6.875%, 6/15/27	0.95
7.	MDC Partners, Inc., 6.5%, 5/1/24 (144A)	0.95
8.	Covanta Holding Corp., 6.0%, 1/1/27	0.91
9.	Crown Cork & Seal Co., Inc., 7.375%, 12/15/26	0.90
10.	Michaels Stores, Inc., 8.0%, 7/15/27 (144A)	0.90

* Excludes temporary cash investments and all derivative contracts except for options purchased. The Fund is actively managed, and current holdings may be different. The holdings listed should not be considered recommendations to buy or sell any securities.

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Prices and Distributions | 10/31/20

Net Asset Value per Share


Class	10/31/20	10/31/19
A	$8.99	$9.58
C	$9.18	$9.79
R	$10.20	$10.84
Y	$9.00	$9.59

Distributions per Share: 11/1/19–10/31/20


	Net Investment	Short-Term	Long-Term
Class	Income	Capital Gains	Capital Gains
A	$0.4939	$ —	$ —
C	$0.4353	$ —	$ —
R	$0.5121	$ —	$ —
Y	$0.5191	$ —	$ —

Index Definitions

The ICE Bank of America (BofA) U.S. High Yield Index is an unmanaged, commonly accepted measure of the performance of high-yield securities. The ICE Bank of America (BofA) All-Convertibles Speculative Quality Index is an unmanaged index of high-yield U.S. convertible securities. Index returns are calculated monthly, assume reinvestment of dividends and, unlike fund returns, do not reflect any fees, expense or sales charges. It is not possible to invest directly in an index.

The indices defined here pertain to the “Value of $10,000 Investment” and the “Value of $5 Million Investment” charts on pages 13–16.

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Performance Update \| 10/31/20	Class A Shares

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class A shares of Pioneer High Yield Fund at public offering price during the periods shown, compared to that of the ICE Bank of America (BofA) U.S. High Yield Index and the ICE BofA All-Convertibles Speculative Quality Index.


Average Annual Total Returns
(As of October 31, 2020)
			ICE	ICE
	Net	Public	BofA	BofA All-
	Asset	Offering	U.S. High	Convertibles
	Value	Price	Yield	Speculative
Period	(NAV)	(POP)	Index	Quality Index
10 years	5.08%	4.60%	6.07%	12.49%
5 years	4.61	3.65	6.14	18.22
1 year	-0.89	-5.35	2.54	61.05


Expense Ratio
(Per prospectus dated March 1, 2020)
Gross		Net
1.19%		1.10%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

NAV results represent the percent change in net asset value per share. POP returns reflect deduction of maximum 4.50% sales charge. NAV returns would have been lower had sales charges been reflected. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The net expense ratio reflects the contractual expense limitation in effect through March 1, 2021 for Class A shares. There can be no assurance that Amundi will extend the expense limitation beyond such time. Please see the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

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Performance Update \| 10/31/20	Class C Shares

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class C shares of Pioneer High Yield Fund during the periods shown, compared to that of the ICE Bank of America (BofA) U.S. High Yield Index and the ICE BofA All-Convertibles Speculative Quality Index.


Average Annual Total Returns
(As of October 31, 2020)
			ICE	ICE
			BofA	BofA All-
			U.S. High	Convertibles
	If	If	Yield	Speculative
Period	Held	Redeemed	Index	Quality Index
10 years	4.34%	4.34%	6.07%	12.49%
5 years	3.84	3.84	6.14	18.22
1 year	-1.71	-1.71	2.54	61.05


Expense Ratio
(Per prospectus dated March 1, 2020)
Gross
1.94%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

Class C shares held for less than one year are also subject to a 1% contingent deferred sales charge (CDSC). “If Held” results represent the percent change in net asset value per share. NAV returns would have been lower had sales charges been reflected. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

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Performance Update \| 10/31/20	Class R Shares

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class R shares of Pioneer High Yield Fund during the periods shown, compared to that of the ICE Bank of America (BofA) U.S. High Yield Index and the ICE BofA All-Convertibles Speculative Quality Index.


Average Annual Total Returns
(As of October 31, 2020)
		ICE	ICE
	Net	BofA	BofA All-
	Asset	U.S. High	Convertibles
	Value	Yield	Speculative
Period	(NAV)	Index	Quality Index
10 years	4.73%	6.07%	12.49%
5 years	4.25	6.14	18.22
1 year	-1.08	2.54	61.05


Expense Ratio
(Per prospectus dated March 1, 2020)
Gross
1.63%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

Class R shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

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Performance Update \| 10/31/20	Class Y Shares

Investment Returns

The mountain chart on the right shows the change in value of a $5 million investment made in Class Y shares of Pioneer High Yield Fund, during the periods shown, compared to that of the ICE Bank of America (BofA) U.S. High Yield Index and the ICE BofA All-Convertibles Speculative Quality Index.


Average Annual Total Returns
(As of October 31, 2020)
		ICE	ICE
	Net	BofA	BofA All-
	Asset	U.S. High	Convertibles
	Value	Yield	Speculative
Period	(NAV)	Index	Quality Index
10 years	5.41%	6.07%	12.49%
5 years	4.91	6.14	18.22
1 year	-0.62	2.54	61.05


Expense Ratio
(Per prospectus dated March 1, 2020)
Gross		Net
0.88%		0.85%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

Class Y shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

The net expense ratio reflects the contractual expense limitation in effect through March 1, 2021 for Class Y shares. There can be no assurance that Amundi will extend the expense limitation beyond such time. Please see the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

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Comparing Ongoing Fund Expenses

As a shareowner in the Fund, you incur two types of costs:

(1)	ongoing costs, including management fees, distribution and/or service (12b-1) fees, and other Fund expenses; and

(2)	transaction costs, including sales charges (loads) on purchase payments.

This example is intended to help you understand your ongoing expenses (in dollars) of investing in the Fund 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 at the beginning of the Fund’s latest six-month period and held throughout the six months.

Using the Tables

Actual Expenses

The first table below provides information about actual account values and actual expenses. You may use the information in this table, together with the amount you invested, to estimate the expenses that you paid over the period as follows:

1.	Divide your account value by $1,000
	Example: an $8,600 account value ÷ $1,000 = 8.6

2.	Multiply the result in (1) above by the corresponding share class’s number in the third row under the heading entitled “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Expenses Paid on a $1,000 Investment in Pioneer High Yield Fund

Based on actual returns from May 1, 2020 through October 31, 2020.


Share Class	A	C	R	Y
Beginning Account	$1,000.00	$1,000.00	$1,000.00	$1,000.00
Value on 5/1/20
Ending Account	$1,124.46	$1,119.60	$1,121.67	$1,127.01
Value (after expenses)
on 10/31/20
Expenses Paid	$5.87	$9.96	$8.05	$4.54
During Period*

* Expenses are equal to the Fund's annualized expense ratio of 1.10%, 1.87%, 1.51%, and 0.85% for Class A, C, R and Y shares, respectively, multiplied by the average account value over the period, multiplied by 184/366 (to reflect the partial year period).

Pioneer High Yield Fund | Annual Report | 10/31/20 17

Table of Contents

Hypothetical Example for Comparison Purposes

The table below provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the Fund’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 Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the tables are meant to highlight your ongoing costs only and do not reflect any transaction costs, such as sales charges (loads) that are charged at the time of the transaction. Therefore, the table below 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 transaction costs were included, your costs would have been higher.

Expenses Paid on a $1,000 Investment in Pioneer High Yield Fund

Based on a hypothetical 5% return per year before expenses, reflecting the period from May 1, 2020 through October 31.


Share Class	A	C	R	Y
Beginning Account	$1,000.00	$1,000.00	$1,000.00	$1,000.00
Value on 5/1/20
Ending Account	$1,019.61	$1,015.74	$1,017.55	$1,020.86
Value (after expenses)
on 10/31/20
Expenses Paid	$5.58	$9.48	$7.66	$4.32
During Period*

18 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents

Schedule of Investments | 10/31/20


Shares		Value
	UNAFFILIATED ISSUERS — 95.3%
	COMMON STOCKS — 0.1% of Net Assets
	Oil, Gas & Consumable Fuels — 0.1%
23	Amplify Energy Corp.	$ 15
6,967,063^+(a)	Ascent CNR Corp.	209,012
30,000(a)	Whiting Petroleum Corp.	438,000
	Total Oil, Gas & Consumable Fuels	$ 647,027
	TOTAL COMMON STOCKS
	(Cost $1,966,916)	$ 647,027
	CONVERTIBLE PREFERRED STOCK — 0.4%
	of Net Assets
	Banks — 0.4%
1,561(b)	Wells Fargo & Co., 7.5%	$ 2,105,414
	Total Banks	$ 2,105,414
	TOTAL CONVERTIBLE PREFERRED STOCK
	(Cost $1,767,832)	$ 2,105,414


Principal
Amount
USD ($)
	ASSET BACKED SECURITY — 0.1% of Net
	Assets
750,000	InSite Issuer LLC, Series 2016-1A, Class C, 6.414%,
	11/15/46 (144A)	$ 803,410
	TOTAL ASSET BACKED SECURITY
	(Cost $750,000)	$ 803,410
	COLLATERALIZED MORTGAGE OBLIGATION —
	0.0%† of Net Assets
220,028	Global Mortgage Securitization, Ltd., Series 2004-A,
	Class B1, 5.25%, 11/25/32 (144A)	$ 129,939
	TOTAL COLLATERALIZED MORTGAGE OBLIGATION
	(Cost $213,090)	$ 129,939
	COMMERCIAL MORTGAGE-BACKED SECURITY —
	0.3% of Net Assets
1,922,620(c)	Banc of America Commercial Mortgage Trust,
	Series 2007-4, Class H, 5.866%, 2/10/51 (144A)	$ 1,750,238
	TOTAL COMMERCIAL MORTGAGE-BACKED SECURITY
	(Cost $1,892,675)	$ 1,750,238
	CONVERTIBLE CORPORATE BONDS — 4.4%
	of Net Assets
	Airlines — 0.8%
2,131,000	Air Canada, 4.0%, 7/1/25 (144A)	$ 2,321,533
1,658,000	Southwest Airlines Co., 1.25%, 5/1/25	2,230,010
	Total Airlines	$ 4,551,543

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 19

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Principal
Amount
USD ($)		Value
	Biotechnology — 0.8%
1,827,000	Exact Sciences Corp., 0.375%, 3/1/28	$ 2,240,359
2,597,000	Insmed, Inc., 1.75%, 1/15/25	2,857,853
	Total Biotechnology	$ 5,098,212
	Commercial Services — 0.2%
1,248,750	Macquarie Infrastructure Corp., 2.0%, 10/1/23	$ 1,134,864
	Total Commercial Services	$ 1,134,864
	Computers — 0.3%
2,070,000	Pure Storage, Inc., 0.125%, 4/15/23	$ 2,019,248
	Total Computers	$ 2,019,248
	Engineering & Construction — 0.3%
1,765,000	Dycom Industries, Inc., 0.75%, 9/15/21	$ 1,720,875
	Total Engineering & Construction	$ 1,720,875
	Healthcare-Products — 0.3%
1,915,000	Integra LifeSciences Holdings Corp., 0.5%,
	8/15/25 (144A)	$ 1,747,437
	Total Healthcare-Products	$ 1,747,437
	Internet — 0.3%
1,755,000	Palo Alto Networks, Inc., 0.375%, 6/1/25 (144A)	$ 1,783,519
	Total Internet	$ 1,783,519
	Leisure Time — 0.2%
915,000	Royal Caribbean Cruises, Ltd., 4.25%, 6/15/23 (144A)	$ 947,891
	Total Leisure Time	$ 947,891
	Media — 0.2%
1,596,000	DISH Network Corp., 3.375%, 8/15/26	$ 1,410,720
	Total Media	$ 1,410,720
	Pharmaceuticals — 0.4%
2,035,000	Revance Therapeutics, Inc., 1.75%, 2/15/27 (144A)	$ 2,164,614
2,122,000	Tricida, Inc., 3.5%, 5/15/27 (144A)	905,578
	Total Pharmaceuticals	$ 3,070,192
	Software — 0.6%
1,714,000	Akamai Technologies, Inc., 0.125%, 5/1/25	$ 2,002,166
2,025,000	Workiva, Inc., 1.125%, 8/15/26	2,004,368
	Total Software	$ 4,006,534
	TOTAL CONVERTIBLE CORPORATE BONDS
	(Cost $26,570,955)	$ 27,491,035

The accompanying notes are an integral part of these financial statements.

20 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents


Principal
Amount
USD ($)		Value
	CORPORATE BONDS — 81.6% of Net Assets
	Advertising — 1.9%
300,000	Clear Channel International BV, 6.625%, 8/1/25 (144A)	$ 304,500
775,000	Lamar Media Corp., 3.75%, 2/15/28	771,869
645,000	Lamar Media Corp., 4.875%, 1/15/29	670,800
5,857,000	MDC Partners, Inc., 6.5%, 5/1/24 (144A)	5,604,095
3,614,000	Outfront Media Capital LLC/Outfront Media Capital
	Corp., 5.625%, 2/15/24	3,641,105
975,000	Outfront Media Capital LLC/Outfront Media Capital
	Corp., 6.25%, 6/15/25 (144A)	995,109
	Total Advertising	$ 11,987,478
	Aerospace & Defense — 0.5%
2,260,000	Howmet Aerospace, Inc., 6.875%, 5/1/25	$ 2,514,250
475,000	Triumph Group, Inc., 8.875%, 6/1/24 (144A)	504,236
	Total Aerospace & Defense	$ 3,018,486
	Airlines — 0.9%
2,809,000	Delta Air Lines, Inc., 3.75%, 10/28/29	$ 2,347,210
225,000	Delta Air Lines, Inc., 7.375%, 1/15/26	232,875
850,000	Delta Air Lines, Inc./SkyMiles IP, Ltd., 4.75%, 10/20/28
	(144A)	868,880
2,430,000	Mileage Plus Holdings LLC/Mileage Plus Intellectual
	Property Assets, Ltd., 6.5%, 6/20/27 (144A)	2,530,238
	Total Airlines	$ 5,979,203
	Apparel — 0.2%
1,180,000	Wolverine World Wide, Inc., 6.375%, 5/15/25 (144A)	$ 1,256,700
	Total Apparel	$ 1,256,700
	Auto Manufacturers — 2.3%
3,110,000	Ford Motor Credit Co. LLC, 4.125%, 8/17/27	$ 3,063,350
3,095,000	Ford Motor Credit Co. LLC, 4.134%, 8/4/25	3,074,294
1,635,000	Ford Motor Credit Co. LLC, 4.542%, 8/1/26	1,663,612
1,825,000	Ford Motor Credit Co. LLC, 5.113%, 5/3/29	1,895,719
4,221,000	JB Poindexter & Co., Inc., 7.125%, 4/15/26 (144A)	4,486,121
	Total Auto Manufacturers	$ 14,183,096
	Auto Parts & Equipment — 1.4%
4,585,000	American Axle & Manufacturing, Inc., 6.25%, 3/15/26	$ 4,595,087
3,003,000	Dealer Tire LLC/DT Issuer LLC, 8.0%, 2/1/28 (144A)	3,070,567
968,000	Goodyear Tire & Rubber Co., 9.5%, 5/31/25	1,064,994
	Total Auto Parts & Equipment	$ 8,730,648
	Banks — 2.6%
1,500,000(b)(c)	Barclays Plc, 7.75% (5 Year USD Swap Rate + 484 bps)	$ 1,546,605
1,575,000(b)(c)	Citigroup, Inc., 4.7% (SOFRRATE + 323 bps)	1,540,547
3,568,000	Freedom Mortgage Corp., 8.125%, 11/15/24 (144A)	3,594,760
2,396,000	Freedom Mortgage Corp., 8.25%, 4/15/25 (144A)	2,421,398

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 21

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Principal
Amount
USD ($)		Value
	Banks — (continued)
1,600,000(b)(c)	Intesa Sanpaolo S.p.A., 7.7% (5 Year USD Swap
	Rate + 546 bps) (144A)	$ 1,688,000
2,195,000(b)(c)	JPMorgan Chase & Co., 4.6% (SOFRRATE + 313 bps)	2,164,270
3,538,000	Provident Funding Associates LP/PFG Finance Corp.,
	6.375%, 6/15/25 (144A)	3,475,643
	Total Banks	$ 16,431,223
	Building Materials — 2.3%
270,000	Builders FirstSource, Inc., 5.0%, 3/1/30 (144A)	$ 284,850
2,553,000	Builders FirstSource, Inc., 6.75%, 6/1/27 (144A)	2,738,092
815,000	Cornerstone Building Brands, Inc., 6.125%,
	1/15/29 (144A)	832,563
585,000	Forterra Finance LLC/FRTA Finance Corp., 6.5%,
	7/15/25 (144A)	617,906
1,670,000	JELD-WEN, Inc., 6.25%, 5/15/25 (144A)	1,782,725
4,458,000	Patrick Industries, Inc., 7.5%, 10/15/27 (144A)	4,829,931
520,000	Standard Industries, Inc., 4.375%, 7/15/30 (144A)	535,600
203,000	Summit Materials LLC/Summit Materials Finance
	Corp., 5.125%, 6/1/25 (144A)	205,538
130,000	Summit Materials LLC/Summit Materials Finance
	Corp., 5.25%, 1/15/29 (144A)	133,900
2,918,000	Summit Materials LLC/Summit Materials Finance
	Corp., 6.5%, 3/15/27 (144A)	3,056,605
	Total Building Materials	$ 15,017,710
	Chemicals — 3.0%
2,607,000	CF Industries, Inc., 5.375%, 3/15/44	$ 3,200,092
2,860,000	Element Solutions, Inc., 3.875%, 9/1/28 (144A)	2,824,250
634,000	Hexion, Inc., 7.875%, 7/15/27 (144A)	657,775
1,800,000	Ingevity Corp., 3.875%, 11/1/28 (144A)	1,827,360
2,080,000	OCI NV, 4.625%, 10/15/25 (144A)	2,106,416
690,000	OCI NV, 5.25%, 11/1/24 (144A)	705,525
1,976,000	Olin Corp., 5.0%, 2/1/30	1,990,820
295,000	Olin Corp., 9.5%, 6/1/25 (144A)	348,873
2,645,000	Tronox, Inc., 6.5%, 5/1/25 (144A)	2,790,475
2,760,000	Tronox, Inc., 6.5%, 4/15/26 (144A)	2,799,358
	Total Chemicals	$ 19,250,944
	Coal — 0.7%
4,474,000	SunCoke Energy Partners LP/SunCoke Energy
	Partners Finance Corp., 7.5%, 6/15/25 (144A)	$ 4,004,230
	Total Coal	$ 4,004,230
	Commercial Services — 5.2%
1,410,000	Allied Universal Holdco LLC/Allied Universal Finance
	Corp., 6.625%, 7/15/26 (144A)	$ 1,477,024
3,405,000	Allied Universal Holdco LLC/Allied Universal Finance
	Corp., 9.75%, 7/15/27 (144A)	3,631,501

The accompanying notes are an integral part of these financial statements.

22 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents


Principal
Amount
USD ($)		Value
	Commercial Services — (continued)
1,710,000	APX Group, Inc., 6.75%, 2/15/27 (144A)	$ 1,782,675
2,030,000	Brink’s Co., 5.5%, 7/15/25 (144A)	2,111,626
4,015,000	Cardtronics, Inc./Cardtronics USA, Inc., 5.5%,
	5/1/25 (144A)	4,050,131
5,985,000	Garda World Security Corp., 9.5%, 11/1/27 (144A)	6,388,987
975,000	Prime Security Services Borrower LLC/Prime
	Finance, Inc., 5.25%, 4/15/24 (144A)	1,019,918
1,870,000	Prime Security Services Borrower LLC/Prime
	Finance, Inc., 5.75%, 4/15/26 (144A)	1,991,550
4,165,000	Prime Security Services Borrower LLC/Prime
	Finance, Inc., 6.25%, 1/15/28 (144A)	4,208,649
2,879,000	Sotheby’s, 7.375%, 10/15/27 (144A)	2,936,580
450,000	United Rentals North America, Inc., 5.25%, 1/15/30	487,688
2,020,000	United Rentals North America, Inc., 5.5%, 5/15/27	2,147,512
	Total Commercial Services	$ 32,233,841
	Computers — 0.6%
1,120,000	Booz Allen Hamilton, Inc., 3.875%, 9/1/28 (144A)	$ 1,136,800
305,000	Diebold Nixdorf, Inc., 9.375%, 7/15/25 (144A)	323,681
1,275,000	NCR Corp., 5.0%, 10/1/28 (144A)	1,262,250
635,000	NCR Corp., 5.25%, 10/1/30 (144A)	628,650
290,000	NCR Corp., 8.125%, 4/15/25 (144A)	319,000
	Total Computers	$ 3,670,381
	Cosmetics/Personal Care — 0.5%
3,080,000	Edgewell Personal Care Co., 5.5%, 6/1/28 (144A)	$ 3,237,018
	Total Cosmetics/Personal Care	$ 3,237,018
	Diversified Financial Services — 1.6%
2,360,000	Alliance Data Systems Corp., 4.75%, 12/15/24 (144A)	$ 2,188,900
2,550,000	Avation Capital SA, 6.5%, 5/15/21 (144A)	1,606,500
3,305,637(d)	Global Aircraft Leasing Co., Ltd., 6.5% (7.25% PIK 6.50%
	cash), 9/15/24 (144A)	2,214,777
835,000	Nationstar Mortgage Holdings, Inc., 5.5%,
	8/15/28 (144A)	832,913
1,160,000	Nationstar Mortgage Holdings, Inc., 9.125%,
	7/15/26 (144A)	1,240,469
1,075,000	OneMain Finance Corp., 8.875%, 6/1/25	1,182,500
857,000	Quicken Loans LLC/Quicken Loans Co.-Issuer, Inc.,
	3.625%, 3/1/29 (144A)	844,145
	Total Diversified Financial Services	$ 10,110,204
	Electric — 1.8%
875,000	Calpine Corp., 4.625%, 2/1/29 (144A)	$ 883,496
875,000	Calpine Corp., 5.0%, 2/1/31 (144A)	893,331
1,691,000	Calpine Corp., 5.25%, 6/1/26 (144A)	1,736,860
995,000	Clearway Energy Operating LLC, 4.75%, 3/15/28 (144A)	1,045,994

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 23

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Principal
Amount
USD ($)		Value
	Electric — (continued)
262,875	NSG Holdings LLC/NSG Holdings, Inc., 7.75%,
	12/15/25 (144A)	$ 278,647
390,000	Pattern Energy Operations LP/Pattern Energy
	Operations, Inc., 4.5%, 8/15/28 (144A)	406,626
2,830,000	Talen Energy Supply LLC, 7.625%, 6/1/28 (144A)	2,769,863
2,852,000	Vistra Operations Co. LLC, 5.625%, 2/15/27 (144A)	2,973,210
	Total Electric	$ 10,988,027
	Electrical Components & Equipment — 1.0%
EUR 1,530,000	Belden, Inc., 3.875%, 3/15/28 (144A)	$ 1,767,712
1,800,000	Energizer Holdings, Inc., 4.75%, 6/15/28 (144A)	1,852,416
1,390,000	WESCO Distribution, Inc., 7.125%, 6/15/25 (144A)	1,497,725
965,000	WESCO Distribution, Inc., 7.25%, 6/15/28 (144A)	1,056,675
	Total Electrical Components & Equipment	$ 6,174,528
	Electronics — 0.1%
795,000	Sensata Technologies, Inc., 3.75%, 2/15/31 (144A)	$ 787,050
	Total Electronics	$ 787,050
	Engineering & Construction — 1.1%
2,070,000	KBR, Inc., 4.75%, 9/30/28 (144A)	$ 2,096,310
4,510,000	PowerTeam Services LLC, 9.033%, 12/4/25 (144A)	4,774,963
	Total Engineering & Construction	$ 6,871,273
	Entertainment — 2.6%
2,936,000	Caesars Entertainment, Inc., 8.125%, 7/1/27 (144A)	$ 3,064,289
942,000	Cirsa Finance International S.a.r.l., 7.875%,
	12/20/23 (144A)	852,510
3,514,000	Enterprise Development Authority, 12.0%,
	7/15/24 (144A)	3,891,755
903,000	Penn National Gaming, Inc., 5.625%, 1/15/27 (144A)	923,498
1,580,000	Scientific Games International, Inc., 7.0%,
	5/15/28 (144A)	1,569,430
1,580,000	Scientific Games International, Inc., 7.25%,
	11/15/29 (144A)	1,567,234
3,958,000	Scientific Games International, Inc., 8.25%,
	3/15/26 (144A)	4,014,956
605,000	SeaWorld Parks & Entertainment, Inc., 9.5%,
	8/1/25 (144A)	635,250
	Total Entertainment	$ 16,518,922
	Environmental Control — 1.4%
5,150,000	Covanta Holding Corp., 6.0%, 1/1/27	$ 5,363,416
3,188,000	Tervita Corp., 7.625%, 12/1/21 (144A)	3,060,480
	Total Environmental Control	$ 8,423,896

The accompanying notes are an integral part of these financial statements.

24 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents


Principal
Amount
USD ($)		Value
	Food — 2.2%
1,890,000	Albertsons Cos., Inc./Safeway, Inc./New Albertsons
	LP/Albertsons LLC, 3.5%, 3/15/29 (144A)	$ 1,833,489
3,217,000	FAGE International SA/FAGE USA Dairy Industry, Inc.,
	5.625%, 8/15/26 (144A)	3,081,500
738,000	Ingles Markets, Inc., 5.75%, 6/15/23	743,535
1,414,000	JBS USA LUX SA/JBS USA Finance, Inc., 6.75%,
	2/15/28 (144A)	1,555,160
1,434,000	JBS USA LUX SA/JBS USA Food Co./JBS USA
	Finance, Inc., 5.5%, 1/15/30 (144A)	1,559,475
4,265,000	Simmons Foods, Inc., 5.75%, 11/1/24 (144A)	4,217,019
805,000	United Natural Foods, Inc., 6.75%, 10/15/28 (144A)	815,063
	Total Food	$ 13,805,241
	Forest Products & Paper — 1.1%
2,030,000	Clearwater Paper Corp., 4.75%, 8/15/28 (144A)	$ 2,040,150
1,883,000	Mercer International, Inc., 7.375%, 1/15/25	1,914,785
3,018,000	Schweitzer-Mauduit International, Inc., 6.875%,
	10/1/26 (144A)	3,183,990
	Total Forest Products & Paper	$ 7,138,925
	Healthcare-Products — 0.2%
1,050,000	Varex Imaging Corp., 7.875%, 10/15/27 (144A)	$ 1,068,375
	Total Healthcare-Products	$ 1,068,375
	Healthcare-Services — 2.2%
1,075,000	Legacy LifePoint Health LLC, 6.75%, 4/15/25 (144A)	$ 1,136,813
1,565,000	Prime Healthcare Services, Inc., 7.25%, 11/1/25 (144A)	1,577,207
475,000	Providence Service Corp., 5.875%, 11/15/25 (144A)	483,313
4,328,000	Surgery Center Holdings, Inc., 10.0%, 4/15/27 (144A)	4,620,140
2,287,000	US Renal Care, Inc., 10.625%, 7/15/27 (144A)	2,435,655
2,821,000	West Street Merger Sub, Inc., 6.375%, 9/1/25 (144A)	2,863,315
	Total Healthcare-Services	$ 13,116,443
	Holding Companies-Diversified — 0.4%
2,900,000	VistaJet Malta Finance Plc/XO Management
	Holding, Inc., 10.5%, 6/1/24 (144A)	$ 2,755,000
	Total Holding Companies-Diversified	$ 2,755,000
	Home Builders — 4.2%
2,000,000	Beazer Homes USA, Inc., 5.875%, 10/15/27	$ 2,030,000
3,790,000	Beazer Homes USA, Inc., 6.75%, 3/15/25	3,894,225
1,405,000	Beazer Homes USA, Inc., 7.25%, 10/15/29	1,509,953
840,000	Brookfield Residential Properties, Inc./Brookfield
	Residential US Corp., 4.875%, 2/15/30 (144A)	798,000
2,573,000	Brookfield Residential Properties, Inc./Brookfield
	Residential US Corp., 6.25%, 9/15/27 (144A)	2,636,553
4,767,000	KB Home, 6.875%, 6/15/27	5,625,060

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 25

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Principal
Amount
USD ($)		Value
	Home Builders — (continued)
3,165,000	M/I Homes, Inc., 4.95%, 2/1/28	$ 3,275,775
2,963,000	Taylor Morrison Communities, Inc., 5.875%,
	6/15/27 (144A)	3,274,115
1,825,000	TRI Pointe Group, Inc., 5.7%, 6/15/28	2,025,750
750,000	Williams Scotsman International, Inc., 4.625%,
	8/15/28 (144A)	754,688
405,000	Winnebago Industries, Inc., 6.25%, 7/15/28 (144A)	428,288
	Total Home Builders	$ 26,252,407
	Household Products/Wares — 0.3%
590,000	Central Garden & Pet Co., 4.125%, 10/15/30	$ 597,375
1,360,000	Spectrum Brands, Inc., 5.5%, 7/15/30 (144A)	1,455,200
	Total Household Products/Wares	$ 2,052,575
	Housewares — 0.1%
445,000	CD&R Smokey Buyer, Inc., 6.75%, 7/15/25 (144A)	$ 469,475
	Total Housewares	$ 469,475
	Internet — 0.9%
1,275,000	ANGI Group LLC, 3.875%, 8/15/28 (144A)	$ 1,260,656
3,907,000	Netflix, Inc., 5.375%, 11/15/29 (144A)	4,576,074
	Total Internet	$ 5,836,730
	Iron & Steel — 1.8%
2,920,000	Carpenter Technology Corp., 6.375%, 7/15/28	$ 3,062,975
4,993,000	Cleveland-Cliffs, Inc., 6.75%, 3/15/26 (144A)	5,242,650
290,000	Cleveland-Cliffs, Inc., 9.875%, 10/17/25 (144A)	331,687
1,230,000	Commercial Metals Co., 5.375%, 7/15/27	1,282,275
1,487,000	Commercial Metals Co., 5.75%, 4/15/26	1,535,327
	Total Iron & Steel	$ 11,454,914
	Leisure Time — 0.8%
500,000	Carnival Corp., 10.5%, 2/1/26 (144A)	$ 541,250
500,000	Royal Caribbean Cruises, Ltd., 9.125%, 6/15/23 (144A)	520,625
1,191,000	Royal Caribbean Cruises, Ltd., 11.5%, 6/1/25 (144A)	1,362,206
2,978,000	Viking Cruises, Ltd., 5.875%, 9/15/27 (144A)	2,322,840
	Total Leisure Time	$ 4,746,921
	Lodging — 1.6%
1,645,000	Boyd Gaming Corp., 8.625%, 6/1/25 (144A)	$ 1,800,781
385,000	Hilton Domestic Operating Co., Inc., 5.375%,
	5/1/25 (144A)	397,851
595,000	Hyatt Hotels Corp., 4.375%, 9/15/28	606,030
1,530,000	Hyatt Hotels Corp., 5.375%, 4/23/25	1,659,329
3,685,000	Station Casinos LLC, 4.5%, 2/15/28 (144A)	3,491,538
1,270,000	Wyndham Destinations, Inc., 6.625%, 7/31/26 (144A)	1,351,217
	Total Lodging	$ 9,306,746

The accompanying notes are an integral part of these financial statements.

26 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents


Principal
Amount
USD ($)		Value
	Media — 3.2%
2,290,000	CCO Holdings LLC/CCO Holdings Capital Corp.,
	5.0%, 2/1/28 (144A)	$ 2,405,645
2,869,000	CCO Holdings LLC/CCO Holdings Capital Corp.,
	5.125%, 5/1/27 (144A)	3,012,450
2,598,000	Clear Channel Worldwide Holdings, Inc., 9.25%, 2/15/24	2,248,231
2,000,000	CSC Holdings LLC, 5.375%, 2/1/28 (144A)	2,125,000
1,040,000	CSC Holdings LLC, 5.75%, 1/15/30 (144A)	1,111,807
2,672,000	CSC Holdings LLC, 7.5%, 4/1/28 (144A)	2,925,479
5,533,000	Diamond Sports Group LLC/Diamond Sports
	Finance Co., 6.625%, 8/15/27 (144A)	2,208,497
526,000	Gray Television, Inc., 5.875%, 7/15/26 (144A)	547,482
3,191,000	Sinclair Television Group, Inc., 5.5%, 3/1/30 (144A)	2,999,859
	Total Media	$ 19,584,450
	Mining — 2.9%
1,689,000	First Quantum Minerals, Ltd., 6.875%, 3/1/26 (144A)	$ 1,676,332
1,680,000	First Quantum Minerals, Ltd., 6.875%, 10/15/27 (144A)	1,675,783
730,000	First Quantum Minerals, Ltd., 7.25%, 4/1/23 (144A)	733,650
375,000	First Quantum Minerals, Ltd., 7.5%, 4/1/25 (144A)	376,875
2,065,000	Hecla Mining Co., 7.25%, 2/15/28	2,214,713
2,280,000	Hudbay Minerals, Inc., 6.125%, 4/1/29 (144A)	2,331,300
3,355,000	IAMGOLD Corp., 5.75%, 10/15/28 (144A)	3,357,684
1,795,000	Joseph T Ryerson & Son, Inc., 8.5%, 8/1/28 (144A)	1,923,432
3,017,000	Novelis Corp., 5.875%, 9/30/26 (144A)	3,113,182
	Total Mining	$ 17,402,951
	Miscellaneous Manufacturers — 0.4%
1,553,000	Bombardier, Inc., 7.5%, 3/15/25 (144A)	$ 1,129,807
1,217,000	Koppers, Inc., 6.0%, 2/15/25 (144A)	1,244,382
	Total Miscellaneous Manufacturers	$ 2,374,189
	Oil & Gas — 5.0%
1,632,000	Aker BP ASA, 3.75%, 1/15/30 (144A)	$ 1,564,622
3,704,000	Baytex Energy Corp., 8.75%, 4/1/27 (144A)	1,629,760
2,325,000	Cenovus Energy, Inc., 5.375%, 7/15/25	2,451,403
2,626,000	Cenovus Energy, Inc., 6.75%, 11/15/39	2,919,890
590,000	EQT Corp., 5.0%, 1/15/29	590,000
3,550,000	Indigo Natural Resources LLC, 6.875%, 2/15/26 (144A)	3,487,875
853,000	MEG Energy Corp., 6.5%, 1/15/25 (144A)	829,543
1,788,000	MEG Energy Corp., 7.0%, 3/31/24 (144A)	1,698,600
1,245,000	MEG Energy Corp., 7.125%, 2/1/27 (144A)	1,120,164
4,499,000	Neptune Energy Bondco Plc, 6.625%, 5/15/25 (144A)	3,914,130
1,790,000	Parkland Corp., 5.875%, 7/15/27 (144A)	1,847,432
1,064,000	Parsley Energy LLC/Parsley Finance Corp., 4.125%,
	2/15/28 (144A)	1,107,145

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 27

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Principal
Amount
USD ($)		Value
	Oil & Gas — (continued)
540,000	Parsley Energy LLC/Parsley Finance Corp., 5.25%,
	8/15/25 (144A)	$ 556,200
1,900,000	Parsley Energy LLC/Parsley Finance Corp., 5.625%,
	10/15/27 (144A)	2,021,125
4,690,000	PBF Holding Co. LLC/PBF Finance Corp., 6.0%,
	2/15/28 (144A)	1,805,416
647,000	PBF Holding Co. LLC/PBF Finance Corp., 9.25%,
	5/15/25 (144A)	574,213
4,889,000	Shelf Drilling Holdings, Ltd., 8.25%, 2/15/25 (144A)	1,613,370
2,000,000	Transocean Sentry, Ltd., 5.375%, 5/15/23 (144A)	1,285,000
523,000	Transocean, Inc., 8.0%, 2/1/27 (144A)	142,518
	Total Oil & Gas	$ 31,158,406
	Oil & Gas Services — 1.3%
1,270,000	Archrock Partners LP/Archrock Partners Finance
	Corp., 6.25%, 4/1/28 (144A)	$ 1,225,550
2,700,000	Archrock Partners LP/Archrock Partners Finance Corp.,
	6.875%, 4/1/27 (144A)	2,646,000
1,448,000	Exterran Energy Solutions LP/EES Finance Corp.,
	8.125%, 5/1/25	1,216,320
4,945,000	FTS International, Inc., 6.25%, 5/1/22	1,384,600
1,920,000	SESI LLC, 7.75%, 9/15/24	441,600
1,300,000	USA Compression Partners LP/USA Compression
	Finance Corp., 6.875%, 9/1/27	1,306,773
	Total Oil & Gas Services	$ 8,220,843
	Packaging & Containers — 2.1%
1,715,000	Ardagh Packaging Finance Plc/Ardagh Holdings
	USA, Inc., 5.25%, 4/30/25 (144A)	$ 1,794,456
870,000	CANPACK SA/Eastern PA Land Investment Holding
	LLC, 3.125%, 11/1/25 (144A)	880,875
4,453,000	Crown Cork & Seal Co., Inc., 7.375%, 12/15/26	5,335,184
4,592,000	Greif, Inc., 6.5%, 3/1/27 (144A)	4,815,860
195,000	Plastipak Holdings, Inc., 6.25%, 10/15/25 (144A)	195,244
	Total Packaging & Containers	$ 13,021,619
	Pharmaceuticals — 3.0%
2,087,000	Bausch Health Americas, Inc., 8.5%, 1/31/27 (144A)	$ 2,281,968
530,000	Bausch Health Cos., Inc., 5.0%, 1/30/28 (144A)	523,841
370,000	Bausch Health Cos., Inc., 5.25%, 1/30/30 (144A)	365,393
198,000	Bausch Health Cos., Inc., 5.875%, 5/15/23 (144A)	197,505
1,250,000	Bausch Health Cos., Inc., 7.0%, 3/15/24 (144A)	1,295,312
893,000	Bausch Health Cos., Inc., 7.0%, 1/15/28 (144A)	944,347
893,000	Bausch Health Cos., Inc., 7.25%, 5/30/29 (144A)	960,596
1,084,000	Endo Dac/Endo Finance LLC/Endo Finco, Inc., 6.0%,
	6/30/28 (144A)	837,390
709,000	Endo Dac/Endo Finance LLC/Endo Finco, Inc., 9.5%,
	7/31/27 (144A)	760,551

The accompanying notes are an integral part of these financial statements.

28 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents


Principal
Amount
USD ($)		Value
	Pharmaceuticals — (continued)
1,700,000	P&L Development LLC/PLD Finance Corp., 7.75%,
	11/15/25 (144A)	$ 1,731,875
2,749,000	Par Pharmaceutical, Inc., 7.5%, 4/1/27 (144A)	2,913,940
5,598,000	Teva Pharmaceutical Finance Netherlands III BV,
	2.8%, 7/21/23	5,309,255
	Total Pharmaceuticals	$ 18,121,973
	Pipelines — 5.1%
4,663,000	American Midstream Partners LP/American Midstream
	Finance Corp., 9.5%, 12/15/21 (144A)	$ 4,523,110
3,068,000	Cheniere Energy, Inc., 4.625%, 10/15/28 (144A)	3,167,710
913,000	DCP Midstream Operating LP, 3.875%, 3/15/23	908,435
3,400,000	DCP Midstream Operating LP, 5.6%, 4/1/44	2,958,000
2,800,000	Delek Logistics Partners LP/Delek Logistics Finance
	Corp., 6.75%, 5/15/25	2,499,000
3,520,000(b)(c)	Energy Transfer Operating LP, 7.125% (5 Year CMT
	Index + 531 bps)	2,877,107
68,000	EnLink Midstream LLC, 5.375%, 6/1/29	58,216
1,375,000	EnLink Midstream Partners LP, 4.15%, 6/1/25	1,182,789
685,000	EnLink Midstream Partners LP, 5.05%, 4/1/45	431,550
1,973,000	EnLink Midstream Partners LP, 5.6%, 4/1/44	1,218,327
1,812,000	Global Partners LP/GLP Finance Corp., 7.0%, 8/1/27	1,865,327
1,781,000	Harvest Midstream I LP, 7.5%, 9/1/28 (144A)	1,767,643
4,325,000	Northriver Midstream Finance LP, 5.625%,
	2/15/26 (144A)	4,283,913
1,985,000	NuStar Logistics LP, 6.375%, 10/1/30	1,997,406
2,200,000	PBF Logistics LP/PBF Logistics Finance Corp.,
	6.875%, 5/15/23	1,727,000
	Total Pipelines	$ 31,465,533
	REITs — 2.7%
6,000,000	Iron Mountain, Inc., 4.875%, 9/15/27 (144A)	$ 6,110,700
1,780,000	iStar, Inc., 4.25%, 8/1/25	1,633,150
3,190,000	iStar, Inc., 4.75%, 10/1/24	3,046,450
2,453,000	MPT Operating Partnership LP/MPT Finance Corp.,
	4.625%, 8/1/29	2,568,291
1,560,000	Uniti Group LP/Uniti Fiber Holdings, Inc./CSL Capital
	LLC, 7.875%, 2/15/25 (144A)	1,655,109
1,585,000	Uniti Group LP/Uniti Group Finance, Inc./CSL Capital
	LLC, 8.25%, 10/15/23	1,561,225
	Total REITs	$ 16,574,925
	Retail — 3.9%
2,660,000	AAG FH LP/AAG FH Finco, Inc., 9.75%, 7/15/24 (144A) $	2,500,400
1,409,000	Asbury Automotive Group, Inc., 4.5%, 3/1/28 (144A)	1,433,657
1,449,000	Asbury Automotive Group, Inc., 4.75%, 3/1/30 (144A)	1,496,092
4,077,000	Beacon Roofing Supply, Inc., 4.875%, 11/1/25 (144A)	3,999,537

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 29

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Principal
Amount
USD ($)		Value
	Retail — (continued)
465,000	Group 1 Automotive, Inc., 4.0%, 8/15/28 (144A)	$ 465,581
880,000	IRB Holding Corp., 7.0%, 6/15/25 (144A)	937,847
865,000	Ken Garff Automotive LLC, 4.875%, 9/15/28 (144A)	857,064
905,000	L Brands, Inc., 6.625%, 10/1/30 (144A)	950,250
5,165,000	Michaels Stores, Inc., 8.0%, 7/15/27 (144A)	5,319,950
1,285,000	Penske Automotive Group, Inc., 3.5%, 9/1/25	1,288,213
1,995,000	QVC, Inc., 4.375%, 9/1/28	1,996,496
2,210,000	QVC, Inc., 4.75%, 2/15/27	2,254,896
1,459,000	Staples, Inc., 7.5%, 4/15/26 (144A)	1,364,165
	Total Retail	$ 24,864,148
	Software — 0.3%
1,875,000	Logan Merger Sub, Inc., 5.5%, 9/1/27 (144A)	$ 1,900,781
	Total Software	$ 1,900,781
	Telecommunications — 3.0%
4,507,000	Altice France Holding SA, 6.0%, 2/15/28 (144A)	$ 4,337,987
465,000	Altice France SA, 5.125%, 1/15/29 (144A)	464,268
800,000	CenturyLink, Inc., 4.0%, 2/15/27 (144A)	817,904
1,996,000	CenturyLink, Inc., 5.8%, 3/15/22	2,075,840
1,510,000	CommScope Technologies LLC, 5.0%, 3/15/27 (144A)	1,409,049
1,081,000	CommScope, Inc., 8.25%, 3/1/27 (144A)	1,118,830
5,850,000	Level 3 Financing, Inc., 4.625%, 9/15/27 (144A)	5,967,000
2,685,000	Windstream Escrow LLC/Windstream Escrow Finance
	Corp., 7.75%, 8/15/28 (144A)	2,591,025
	Total Telecommunications	$ 18,781,903
	Transportation — 1.0%
2,200,000	Watco Cos., LLC/Watco Finance Corp., 6.5%,
	6/15/27 (144A)	$ 2,282,500
3,590,000	Western Global Airlines LLC, 10.375%, 8/15/25 (144A)	3,715,578
	Total Transportation	$ 5,998,078
	Trucking & Leasing — 0.2%
1,205,000	Fortress Transportation & Infrastructure Investors LLC,
	9.75%, 8/1/27 (144A)	$ 1,281,819
	Total Trucking & Leasing	$ 1,281,819
	TOTAL CORPORATE BONDS
	(Cost $513,081,812)	$ 507,630,228
	INSURANCE-LINKED SECURITIES — 0.8%
	of Net Assets^#
	Event Linked Bonds — 0.1%
	Earthquakes – Peru — 0.0%†
245,000(e)	International Bank for Reconstruction & Development,
	6.08% (3 Month USD LIBOR + 600 bps),
	2/15/21 (144A)	$ 245,490

The accompanying notes are an integral part of these financial statements.

30 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents


Principal
Amount
USD ($)		Value
	Multiperil – U.S. — 0.0%†
750,000+(e)	Caelus Re V, 0.586% (1 Month U.S. Treasury Bill +
	50 bps), 6/5/24 (144A)	$ 66
450,000(e)	Caelus Re V, 7.24% (3 Month U.S. Treasury Bill +
	724 bps), 6/7/21 (144A)	180,000
		$ 180,066
	Multiperil – Worldwide — 0.1%
250,000(e)	Galilei Re, 8.674% (6 Month USD LIBOR + 863 bps),
	1/8/21 (144A)	$ 249,125
	Total Event Linked Bonds	$ 674,681


Face
Amount
USD ($)
	Collateralized Reinsurance — 0.3%
	Multiperil – Worldwide — 0.2%
1,000,000+(a)(f)	Cypress Re 2017, 1/10/21	$ 18,200
555,123+(a)(f)	Dartmouth Re 2018, 1/15/21	119,907
250,000+(f)	Dingle Re 2019, 2/1/21	5,132
584,814+(a)(f)	Gloucester Re 2018, 2/28/21	102,927
24,000+(f)	Limestone Re 2016-1, 8/31/21	391
24,000+(f)	Limestone Re 2016-1, 8/31/21	391
39,000+(a)(f)	Limestone Re 2019-2, 3/1/23 (144A)	66,674
333,342+(a)(f)	Oyster Bay Re 2018, 1/15/21	302,541
800,000+(a)(f)	Resilience Re, 4/6/21	80
340,299+(a)(f)	Seminole Re 2018, 1/15/21	10,099
442,599+(a)(f)	Walton Health Re 2018, 6/15/21	210,235
		$ 836,577
	Windstorm – Florida — 0.1%
400,000+(a)(f)	Formby Re 2018, 2/28/21	$ 70,767
750,000+(a)(f)	Portrush Re 2017, 6/15/21	478,575
		$ 549,342
	Windstorm – U.S. Regional — 0.0%†
500,000+(a)(f)	Oakmont Re 2017, 4/30/21	$ 14,700
350,000+(a)(f)	Oakmont Re 2019, 4/30/21	242,309
		$ 257,009
	Total Collateralized Reinsurance	$ 1,642,928
	Reinsurance Sidecars — 0.4%
	Multiperil – U.S. — 0.0%†
1,500,000+(a)(f)	Carnoustie Re 2017, 11/30/21	$ 197,700
1,400,000+(a)(g)	Harambee Re 2018, 12/31/21	11,480
973,488+(g)	Harambee Re 2019, 12/31/22	11,195
		$ 220,375

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 31

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Face
Amount
USD ($)		Value
	Multiperil – Worldwide — 0.4%
8,504+(f)	Alturas Re 2019-2, 3/10/22	$ 45,380
1,000,000+(a)(f)	Bantry Re 2016, 3/31/21	80,600
500,000+(a)(f)	Bantry Re 2017, 3/31/21	118,050
400,000+(a)(f)	Bantry Re 2018, 12/31/21	4,560
400,000+(f)	Bantry Re 2019, 12/31/22	13,585
2,152,482+(a)(f)	Berwick Re 2018-1, 12/31/21	261,957
1,067,182+(a)(f)	Berwick Re 2019-1, 12/31/22	127,528
400,000+(g)	Blue Lotus Re 2018, 12/31/21	17,480
15,000+(f)	Eden Re II, 3/22/22 (144A)	10,328
37,500+(f)	Eden Re II, 3/22/22 (144A)	24,908
7,850+(a)(f)	Eden Re II, 3/22/23 (144A)	67,385
2,400,000+(a)(f)	Gleneagles Re 2016, 11/30/20	74,880
400,000+(a)(f)	Gleneagles Re 2018, 12/31/21	47,320
800,000+(a)(g)	Lorenz Re 2018, 7/1/21	21,920
411,569+(a)(g)	Lorenz Re 2019, 6/30/22	39,799
900,000+(a)(f)	Merion Re 2018-2, 12/31/21	999,556
2,000,000+(f)	Pangaea Re 2016-2, 11/30/20	3,567
500,000+(a)(f)	Pangaea Re 2018-1, 12/31/21	10,527
500,000+(a)(f)	Pangaea Re 2018-3, 7/1/22	10,372
409,624+(a)(f)	Pangaea Re 2019-1, 2/1/23	8,536
367,657+(a)(f)	Pangaea Re 2019-3, 7/1/23	13,225
1,000,000+(a)(f)	St. Andrews Re 2017-1, 2/1/21	67,800
868,992+(a)(f)	St. Andrews Re 2017-4, 6/1/21	85,509
250,000+(a)(g)	Thopas Re 2018, 12/31/21	6,100
600,000+(a)(g)	Thopas Re 2019, 12/31/22	111,000
1,100,000+(a)(f)	Versutus Re 2017, 11/30/21	—
450,000+(a)(f)	Versutus Re 2018, 12/31/21	8,550
397,146+(f)	Versutus Re 2019-A, 12/31/21	17,752
52,853+(f)	Versutus Re 2019-B, 12/31/21	2,362
300,000+(a)(g)	Viribus Re 2018, 12/31/21	10,920
127,384+(g)	Viribus Re 2019, 12/31/22	5,146
405,831+(a)(f)	Woburn Re 2018, 12/31/21	37,391
419,863+(a)(f)	Woburn Re 2019, 12/31/22	143,065
		$ 2,497,058
	Total Reinsurance Sidecars	$ 2,717,433
	TOTAL INSURANCE-LINKED SECURITIES
	(Cost $6,900,578)	$ 5,035,042

The accompanying notes are an integral part of these financial statements.

32 Pioneer High Yield Fund | Annual Report | 10/31/20

Table of Contents


Principal
Amount
USD ($)		Value
	SENIOR SECURED FLOATING RATE LOAN
	INTERESTS — 2.6% of Net Assets*(e)
	Automobile — 0.2%
1,460,813	First Brands Group LLC, First Lien Tranche B-3 Term
	Loan, 8.5% (LIBOR + 750 bps), 2/2/24	$ 1,440,726
	Total Automobile	$ 1,440,726
	Buildings & Real Estate — 0.0%†
266,969	Builders FirstSource, Inc., Refinancing Term Loan, 4.0%
	(LIBOR + 300 bps), 2/29/24	$ 265,968
	Total Buildings & Real Estate	$ 265,968
	Diversified & Conglomerate Service — 0.6%
1,610,056	DynCorp International, Inc., Term Loan, 7.0%
	(LIBOR + 600 bps), 8/18/25	$ 1,602,005
1,913,131	Team Health Holdings, Inc., Initial Term Loan, 3.75%
	(LIBOR + 275 bps), 2/6/24	1,563,985
	Total Diversified & Conglomerate Service	$ 3,165,990
	Healthcare, Education & Childcare — 0.8%
793,486	Alliance HealthCare Services, Inc., First Lien Initial Term
	Loan, 5.5% (LIBOR + 450 bps), 10/24/23	$ 726,039
3,229,949	LifePoint Health, Inc. (fka Regionalcare Hospital
	Partners Holdings, Inc.), First Lien Term B Loan,
	3.898% (LIBOR + 375 bps), 11/16/25	3,141,125
1,049,725	Surgery Center Holdings, Inc., 2020 Incremental
	Term Loan, 9.0% (LIBOR + 800 bps), 9/3/24	1,070,720
	Total Healthcare, Education & Childcare	$ 4,937,884
	Machinery — 0.3%
2,072,685	Shape Technologies Group, Inc., Initial Term Loan,
	3.149% (LIBOR + 300 bps), 4/21/25	$ 1,587,331
	Total Machinery	$ 1,587,331
	Media — 0.0%†
471,530	Diamond Sports Group LLC, Term Loan, 3.4% (LIBOR +
	325 bps), 8/24/26	$ 295,148
	Total Media	$ 295,148
	Securities & Trusts — 0.6%
3,538,286	Spectacle Gary Holdings LLC, Closing Date Term
	Loan, 11.0% (LIBOR + 900 bps), 12/23/25	$ 3,354,738
	Total Securities & Trusts	$ 3,354,738
	Utilities — 0.1%
872,813	PG&E Corp., Term Loan, 5.5% (LIBOR +
	450 bps), 6/23/25	$ 867,903
	Total Utilities	$ 867,903
	TOTAL SENIOR SECURED FLOATING RATE
	LOAN INTERESTS
	(Cost $16,584,505)	$ 15,915,688

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 33

Table of Contents

Schedule of Investments | 10/31/20 (continued)


Principal
Amount
USD ($)		Value
	U.S. GOVERNMENT AND AGENCY OBLIGATIONS —
	5.0% of Net Assets
22,000,000(h)	U.S. Treasury Bills, 11/17/20	$ 21,999,342
9,000,000(e)	U.S. Treasury Floating Rate Notes, 0.4% (3 Month U.S.
	Treasury Bill Money Market Yield +
	30 bps), 10/31/21	9,025,539
	TOTAL U.S. GOVERNMENT AND AGENCY OBLIGATIONS
	(Cost $31,009,215)	$ 31,024,881


Shares
	RIGHTS/WARRANTS — 0.0%† of Net Assets
	Health Care Providers & Services — 0.0%†
2,136^(a)(i)	Option Care Health, Inc., 6/30/25	$ 1,794
2,136^(a)(j)	Option Care Health, Inc., 6/30/25	1,389
	Total Health Care Providers & Services	$ 3,183
	Oil, Gas & Consumable Fuels — 0.0%†
4,728,525(k)	ANR, Inc., 3/31/23	$ 14,185
921(a)(l)	Contura Energy, Inc., 7/26/23	594
	Total Oil, Gas & Consumable Fuels	$ 14,779
	Transportation — 0.0%
17,624^+(a)(m)	Syncreon Group, 10/01/24	$ —
	Total Transportation	$ —
	TOTAL RIGHTS/WARRANTS
	(Cost $598,118)	$ 17,962
	TOTAL INVESTMENTS IN UNAFFILIATED ISSUERS — 95.3%
	(Cost $601,335,696)	$ 592,550,864
	OTHER ASSETS AND LIABILITIES — 4.7%	$ 29,522,523
	NET ASSETS — 100.0%	$ 622,073,387


bps	Basis Points.
CMT	Constant Maturity Rate Index.
LIBOR	London Interbank Offered Rate.
REIT	Real Estate Investment Trust.
SOFRRATE	Secured Overnight Financing Rate.
(144A)	Security is exempt from registration under Rule 144A of the Securities Act of 1933. Such securities may be resold normally to qualified institutional buyers in a transaction exempt from registration. At October 31, 2020, the value of these securities amounted to $386,541,667 or 62.1% of net assets.
†	Amount rounds to less than 0.1%.

The accompanying notes are an integral part of these financial statements.

34 Pioneer High Yield Fund | Annual Report | 10/31/20

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*	Senior secured floating rate loan interests in which the Fund invests generally pay interest at rates that are periodically redetermined by reference to a base lending rate plus a premium. These base lending rates are generally (i) the lending rate offered by one or more major European banks, such as LIBOR, (ii) the prime rate offered by one or more major United States banks, (iii) the rate of a certificate of deposit or (iv) other base lending rates used by commercial lenders. The interest rate shown is the rate accruing at October 31, 2020.
+	Security that used significant unobservable inputs to determine its value.
^	Security is valued using fair value methods (other than supplied by independent pricing services).
(a)	Non-income producing security.
(b)	Security is perpetual in nature and has no stated maturity date.
(c)	The interest rate is subject to change periodically. The interest rate and/or reference index and spread shown at October 31, 2020.
(d)	Payment-in-kind (PIK) security which may pay interest in the form of additional principal amount.
(e)	Floating rate note. Coupon rate, reference index and spread shown at October 31, 2020.
(f)	Issued as participation notes.
(g)	Issued as preference shares.
(h)	Security issued with a zero coupon. Income is recognized through accretion of discount.
(i)	Option Care Health, Inc. warrants are exercisable into 2,136 shares.
(j)	Option Care Health, Inc. warrants are exercisable into 2,136 shares.
(k)	ANR, Inc. warrants are exercisable into 4,728,525 shares.
(l)	Contura Energy, Inc. warrants are exercisable into 921 shares.
(m)	Syncreon Group warrants are exercisable into 17,624 shares.
#	Securities are restricted as to resale.


Restricted Securities	Acquisition date	Cost		Value
Alturas Re 2019-2	12/19/2018	$	8,504	$	45,380
Bantry Re 2016	2/6/2019		80,600		80,600
Bantry Re 2017	2/6/2019		118,062		118,050
Bantry Re 2018	2/6/2019		4,551		4,560
Bantry Re 2019	2/1/2019		—		13,585
Berwick Re 2018-1	1/10/2018		410,080		261,957
Berwick Re 2019-1	12/31/2018		127,519		127,528
Blue Lotus Re 2018	12/20/2017		—		17,480
Caelus Re V	4/27/2017		750,000		66
Caelus Re V	5/4/2018		450,000		180,000
Carnoustie Re 2017	1/5/2017		356,635		197,700
Cypress Re 2017	1/24/2017		3,361		18,200
Dartmouth Re 2018	1/18/2018		228,359		119,907
Dingle Re 2019	3/4/2019		—		5,132
Eden Re II	12/15/2017		896		10,328
Eden Re II	1/23/2018		867		24,908
Eden Re II	1/22/2019		7,850		67,385
Formby Re 2018	7/9/2018		59,220		70,767
Galilei Re	1/4/2017		250,000		249,125
Gleneagles Re 2016	1/14/2016		—		74,880
Gleneagles Re 2018	12/27/2017		32,109		47,320
Gloucester Re 2018	1/2/2018		94,770		102,927

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 35

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Schedule of Investments | 10/31/20 (continued)


Restricted Securities	Acquisition date	Cost		Value
Harambee Re 2018	12/19/2017	$	109,266	$	11,480
Harambee Re 2019	4/24/2019		—		11,195
International Bank for Reconstruction &
Development	2/2/2018		245,000		245,490
Limestone Re 2016-1	12/15/2016		1,980		391
Limestone Re 2016-1	12/15/2016		1,980		391
Limestone Re 2019-2	6/20/2018		39,000		66,674
Lorenz Re 2018	6/26/2018		214,627		21,920
Lorenz Re 2019	7/10/2019		133,882		39,799
Merion Re 2018-2	12/28/2017		900,000		999,556
Oakmont Re 2017	5/10/2017		—		14,700
Oakmont Re 2019	5/21/2019		203,586		242,309
Oyster Bay Re 2018	1/17/2018		297,524		302,541
Pangaea Re 2016-2	5/31/2016		—		3,567
Pangaea Re 2018-1	1/11/2018		71,503		10,527
Pangaea Re 2018-3	5/31/2018		120,430		10,372
Pangaea Re 2019-1	1/9/2019		4,301		8,536
Pangaea Re 2019-3	7/25/2019		11,030		13,225
Portrush Re 2017	6/12/2017		575,238		478,575
Resilience Re	4/13/2017		2,614		80
Seminole Re 2018	1/2/2018		4,563		10,099
St. Andrews Re 2017-1	1/5/2017		67,748		67,800
St. Andrews Re 2017-4	3/31/2017		—		85,509
Thopas Re 2018	12/12/2017		40,037		6,100
Thopas Re 2019	12/21/2018		102,298		111,000
Versutus Re 2017	1/5/2017		72,865		—
Versutus Re 2018	1/31/2018		15,284		8,550
Versutus Re 2019-A	1/28/2019		—		17,752
Versutus Re 2019-B	12/24/2018		—		2,362
Viribus Re 2018	12/22/2017		39,701		10,920
Viribus Re 2019	3/25/2019		—		5,146
Walton Health Re 2018	6/25/2018		362,935		210,235
Woburn Re 2018	3/20/2018		151,224		37,391
Woburn Re 2019	1/30/2019		128,579		143,065
Total Restricted Securities				$	5,035,042
% of Net assets					0.8	%

FORWARD FOREIGN CURRENCY EXCHANGE CONTRACT


Currency		Currency			Settlement	Unrealized
Purchased	In Exchange for	Sold	Deliver	Counterparty	Date	Appreciation
USD	1,720,120	EUR	(1,470,750)	JPMorgan
				Chase Bank NA	11/24/20	$ 6,716
TOTAL FORWARD FOREIGN CURRENCY EXCHANGE CONTRACT						$ 6,716

The accompanying notes are an integral part of these financial statements.

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SWAP CONTRACTS

CENTRALLY CLEARED CREDIT DEFAULT SWAP CONTRACTS — SELL PROTECTION


	Reference		Annual		Premiums	Unrealized
Notional	Obligation/	Pay/	Fixed	Expiration	Paid/	Appreciation	Market
Amount ($)⁽¹⁾	Index	Receive⁽²⁾	Rate	Date	(Received)	(Depreciation)	Value
5,286,600	Markit CDX	Receive	5.00%	6/20/24	$ (50,663)	$ 319,453	$268,790
	North America
	High Yield Index
	Series 32
3,177,300	Markit CDX	Receive	5.00%	12/20/24	75,461	93,334	168,795
	North America
	High Yield Index
	Series 33
9,620,000	Markit CDX	Receive	5.00%	12/20/25	593,073	(215,547)	377,526
	North America
	High Yield Index
	Series 35
TOTAL CENTRALLY CLEARED CREDIT DEFAULT
SWAP CONTRACTS – SELL PROTECTION					$617,871	$ 197,240	$815,111
TOTAL SWAP CONTRACTS					$617,871	$ 197,240	$815,111

⁽¹⁾	The notional amount is the maximum amount that a seller of credit protection would be obligated to pay upon occurrence of a credit event.
⁽²⁾	Receives quarterly.

Principal amounts are denominated in U.S. dollars (“USD”) unless otherwise noted.

EUR — Euro

Purchases and sales of securities (excluding temporary cash investments) for the year ended October 31, 2020 were as follows:


	Purchases		Sales
Long-Term U.S. Government Securities	$	51,141,934	$	42,114,525
Other Long-Term Securities	$	482,967,292	$	575,142,738

The Fund is permitted to engage in purchase and sale transactions (“cross trades”) with certain funds and accounts for which Amundi Pioneer Asset Management, Inc. (the “Adviser”) serves as the Fund’s investment adviser, as set forth in Rule 17a-7 under the Investment Company Act of 1940, pursuant to procedures adopted by the Board of Trustees. Under these procedures, cross trades are effected at current market prices. During the year ended October 31, 2020, the Fund engaged in purchases of $7,026,811 and sales of $9,580,101 pursuant to these procedures, which resulted in a net realized gain/(loss) of $304,044.

At October 31, 2020, the net unrealized depreciation on investments based on cost for federal tax purposes of $603,180,904 was as follows:


Aggregate gross unrealized appreciation for all investments in which
there is an excess of value over tax cost	$	24,522,546
Aggregate gross unrealized depreciation for all investments in which
there is an excess of tax cost over value		(34,330,759	)
Net unrealized depreciation	$	(9,808,213	)

The accompanying notes are an integral part of these financial statements.

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Schedule of Investments | 10/31/20 (continued)

Various inputs are used in determining the value of the Fund’s investments. These inputs are summarized in the three broad levels below.

Level 1 – quoted prices in active markets for identical securities.

Level 2 – other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.). See Notes to Financial Statements — Note 1A.

Level 3 – significant unobservable inputs (including the Fund’s own assumptions in determining fair value of investments). See Notes to Financial Statements — Note 1A.

The following is a summary of the inputs used as of October 31, 2020, in valuing the Fund’s investments:


	Level 1		Level 2		Level 3			Total
Common Stocks
Oil, Gas & Consumable Fuels	$	438,015	$	—	$	209,012		$	647,027
Convertible Preferred Stock		2,105,414		—		—			2,105,414
Asset Backed Security		—		803,410		—			803,410
Collateralized Mortgage
Obligation		—		129,939		—			129,939
Commercial Mortgage-Backed
Security		—		1,750,238		—			1,750,238
Convertible Corporate Bonds		—		27,491,035		—			27,491,035
Corporate Bonds		—		507,630,228		—			507,630,228
Insurance-Linked Securities
Event Linked Bonds
Multiperil - U.S.		—		180,000		66			180,066
Collateralized Reinsurance
Multiperil - Worldwide		—		—		836,577			836,577
Windstorm - Florida		—		—		549,342			549,342
Windstorm - U.S. Regional		—		—		257,009			257,009
Reinsurance Sidecars
Multiperil - U.S.		—		—		220,375			220,375
Multiperil - Worldwide		—		—		2,497,058			2,497,058
All Other Insurance-Linked
Securities		—		494,615		—			494,615
Senior Secured Floating Rate
Loan Interests		—		15,915,688		—			15,915,688
U.S. Government and Agency
Obligations		—		31,024,881		—			31,024,881
Rights/Warrants
Transportation		—		—		—	*		—	*
All Other Rights/Warrants		—		17,962		—			17,962
Total Investments in Securities	$	2,543,429	$	585,437,996	$	4,569,439		$	592,550,864
Other Financial Instruments
Net unrealized appreciation
on forward foreign currency
exchange contracts	$	—	$	6,716	$	—		$	6,716
Swap contracts, at value		—		815,111		—			815,111
Total Other
Financial Instruments	$	—	$	821,827	$	—		$	821,827

* Security valued at $0.

The accompanying notes are an integral part of these financial statements.

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The following is a reconciliation of assets valued using significant unobservable inputs (Level 3):


				Insurance-
	Common			Linked			Rights/
	Stocks			Securities			Warrants			Total
Balance as of 10/31/19	$	1,045,059		$	15,557,184		$	4,486		$	16,606,729
Realized gain (loss)¹		—			(378,194	)		—			(378,194	)
Change in unrealized appreciation
(depreciation)²		(836,047	)		(280,372	)		—			(1,116,419	)
Accrued discounts/premiums		—			—			—			—
Purchases		—			—			—			—
Sales		—			(10,538,266	)		—			(10,538,266	)
Transfers in to Level 3*		—			75			—			75
Transfers out of Level 3*		—			—			(4,486	)		(4,486	)
Balance as of 10/31/20	$	209,012		$	4,360,427		$	—	**	$	4,569,439


¹	Realized gain (loss) on these securities is included in the realized gain (loss) from investments on the Statement of Operations.
²	Unrealized appreciation (depreciation) on these securities is included in the change in unrealized appreciation (depreciation) from investments on the Statement of Operations.
*	Transfers are calculated on the beginning of period value. During the year ended October 31, 2020, an investment valued at $4,486 was transferred from Level 3 to Level 2, as there were significant observable inputs to determine its value. An investment valued at $75 was transferred from Level 2 to Level 3, due to valuing the security using unobservable inputs. There were no other transfers between Levels 1, 2 and 3.
**	Security valued at $0.


Net change in unrealized appreciation (depreciation) of Level 3 investments still
held and considered Level 3 at October 31, 2020:	$	(1,008,299	)

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 39

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Statement of Assets and Liabilities | 10/31/20


ASSETS:
Investments in unaffiliated issuers, at value (cost $601,335,696)	$	592,550,864
Cash		18,177,386
Foreign currencies, at value (cost $44)		44
Swaps collateral		1,955,791
Net unrealized appreciation on forward foreign currency
exchange contracts		6,716
Swap contracts, at value (net premiums paid $617,871)		815,111
Receivables —
Investment securities sold		5,585,008
Fund shares sold		933,946
Interest		8,429,160
Due from the Adviser		170,978
Other assets		39,440
Total assets	$	628,664,444
LIABILITIES:
Payables —
Investment securities purchased	$	3,594,999
Fund shares repurchased		1,487,107
Distributions		271,093
Trustees’ fees		3,790
Transfer agent fees		138,268
Due to broker for swaps		834,890
Variation margin for centrally cleared swap contracts		19,286
Unrealized depreciation on unfunded loan commitments		1,933
Due to affiliates		103,017
Accrued expenses		136,674
Total liabilities	$	6,591,057
NET ASSETS:
Paid-in capital	$	692,149,973
Distributable earnings (loss)		(70,076,586	)
Net assets	$	622,073,387
NET ASSET VALUE PER SHARE:
No par value (unlimited number of shares authorized)
Class A (based on $417,137,491/46,396,523 shares)	$	8.99
Class C (based on $17,018,602/1,852,894 shares)	$	9.18
Class R (based on $11,555,749/1,132,781 shares)	$	10.20
Class Y (based on $176,361,545/19,594,242 shares)	$	9.00
MAXIMUM OFFERING PRICE PER SHARE:
Class A (based on $8.99 net asset value per share/100%-4.50%
maximum sales charge)	$	9.41

The accompanying notes are an integral part of these financial statements.

40 Pioneer High Yield Fund | Annual Report | 10/31/20

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Statement of Operations
FOR THE YEAR ENDED 10/31/20


INVESTMENT INCOME:
Interest from unaffiliated issuers	$	41,258,423
Dividends from unaffiliated issuers		838,304
Total investment income				$	42,096,727
EXPENSES:
Management fees	$	4,562,592
Administrative expense		230,971
Transfer agent fees
Class A		499,947
Class C		10,521
Class R		27,218
Class Y		145,802
Distribution fees
Class A		1,119,947
Class C		200,662
Class R		65,545
Shareowner communications expense		96,587
Custodian fees		37,174
Registration fees		93,092
Professional fees		92,550
Printing expense		61,132
Pricing fees		16,874
Trustees’ fees		33,254
Insurance expense		11,186
Miscellaneous		99,966
Total expenses				$	7,405,020
Less fees waived and expenses reimbursed
by the Adviser					(354,902	)
Net expenses				$	7,050,118
Net investment income				$	35,046,609
REALIZED AND UNREALIZED GAIN (LOSS) ON INVESTMENTS:
Net realized gain (loss) on:
Investments in unaffiliated issuers	$	(28,673,566	)
Forward foreign currency exchange contracts		13,428
Swap contracts		(2,801,079	)
Other assets and liabilities denominated in
foreign currencies		(4,929	)	$	(31,466,146	)
Change in net unrealized appreciation (depreciation) on:
Investments in unaffiliated issuers	$	(13,973,728	)
Forward foreign currency exchange contracts		34,824
Swap contracts		(199,628	)
Unfunded loan commitments		(1,933	)
Other assets and liabilities denominated in
foreign currencies		(259	)	$	(14,140,724	)
Net realized and unrealized gain (loss) on investments				$	(45,606,870	)
Net decrease in net assets resulting from operations				$	(10,560,261	)

The accompanying notes are an integral part of these financial statements.

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Statements of Changes in Net Assets


	Year			Year
	Ended			Ended
	10/31/20			10/31/19
FROM OPERATIONS:
Net investment income (loss)	$	35,046,609		$	38,126,876
Net realized gain (loss) on investments		(31,466,146	)		349,126
Change in net unrealized appreciation (depreciation)
on investments		(14,140,724	)		18,358,078
Net increase (decrease) in net assets resulting
from operations	$	(10,560,261	)	$	56,834,080
DISTRIBUTIONS TO SHAREOWNERS:
Class A ($0.49 and $0.50 per share, respectively)	$	(24,460,968	)	$	(27,353,521	)
Class C ($0.44 and $0.43 per share, respectively)		(945,818	)		(1,370,527	)
Class R ($0.51 and $0.52 per share, respectively)		(653,441	)		(826,025	)
Class Y ($0.52 and $0.53 per share, respectively)		(10,462,395	)		(11,125,229	)
Total distributions to shareowners	$	(36,522,622	)	$	(40,675,302	)
FROM FUND SHARE TRANSACTIONS:
Net proceeds from sales of shares	$	117,065,142		$	90,623,149
Reinvestment of distributions		32,635,161			36,323,782
Cost of shares repurchased		(233,282,658	)		(189,767,932	)
Net decrease in net assets resulting from Fund
share transactions	$	(83,582,355	)	$	(62,821,001	)
Net decrease in net assets	$	(130,665,238	)	$	(46,662,223	)
NET ASSETS:
Beginning of year	$	752,738,625		$	799,400,848
End of year	$	622,073,387		$	752,738,625

The accompanying notes are an integral part of these financial statements.

42 Pioneer High Yield Fund | Annual Report | 10/31/20

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	Year Ended			Year Ended			Year Ended			Year Ended
	10/31/20			10/31/20			10/31/19			10/31/19
	Shares			Amount			Shares			Amount
Class A
Shares sold		3,344,386		$	30,056,468			4,849,062		$	45,650,507
Reinvestment of
distributions		2,422,438			21,857,768			2,599,500			24,355,870
Less shares repurchased		(12,899,513	)		(116,623,759	)		(11,324,747	)		(106,274,058	)
Net decrease		(7,132,689	)	$	(64,709,523	)		(3,876,185	)	$	(36,267,681	)
Class C
Shares sold		219,693		$	2,031,254			233,303		$	2,227,808
Reinvestment of
distributions		94,984			876,231			130,448			1,245,101
Less shares repurchased		(931,263	)		(8,524,422	)		(1,819,086	)		(17,422,957	)
Net decrease		(616,586	)	$	(5,616,937	)		(1,455,335	)	$	(13,950,048	)
Class R
Shares sold		643,180		$	6,436,926			454,405		$	4,836,541
Reinvestment of
distributions		61,475			628,831			72,509			769,145
Less shares repurchased		(986,466	)		(9,978,755	)		(846,914	)		(9,036,019	)
Net decrease		(281,811	)	$	(2,912,998	)		(320,000	)	$	(3,430,333	)
Class Y
Shares sold		8,889,838		$	78,540,494			4,029,145		$	37,908,293
Reinvestment of
distributions		1,028,209			9,272,331			1,061,104			9,953,666
Less shares repurchased		(11,247,935	)		(98,155,722	)		(6,083,115	)		(57,034,898	)
Net decrease		(1,329,888	)	$	(10,342,897	)		(992,866	)	$	(9,172,939	)

The accompanying notes are an integral part of these financial statements.

Pioneer High Yield Fund | Annual Report | 10/31/20 43

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Financial Highlights


	Year			Year			Year			Year			Year
	Ended			Ended			Ended			Ended			Ended
	10/31/20			10/31/19			10/31/18			10/31/17			10/31/16*
Class A
Net asset value, beginning of period	$	9.58		$	9.37		$	9.80		$	9.43		$	9.33
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.48		$	0.47		$	0.47		$	0.46		$	0.46
Net realized and unrealized gain (loss) on investments		(0.58	)		0.24			(0.45	)		0.38			0.19
Net increase (decrease) from investment operations	$	(0.10	)	$	0.71		$	0.02		$	0.84		$	0.65
Distributions to shareowners:
Net investment income	$	(0.49	)	$	(0.50	)	$	(0.45	)	$	(0.47	)	$	(0.48	)
Net realized gain		—			—			—			—			(0.07	)
Total distributions	$	(0.49	)	$	(0.50	)	$	(0.45	)	$	(0.47	)	$	(0.55	)
Net increase (decrease) in net asset value	$	(0.59	)	$	0.21		$	(0.43	)	$	0.37		$	0.10
Net asset value, end of period	$	8.99		$	9.58		$	9.37		$	9.80		$	9.43
Total return (b)		(0.89	)%		7.82	%		0.21	%		9.05	%(c)		7.29	%
Ratio of net expenses to average net assets		1.10	%		1.19	%		1.14	%		1.15	%		1.17	%
Ratio of net investment income (loss) to average net assets		5.24	%		4.97	%		4.87	%		4.80	%		5.09	%
Portfolio turnover rate		85	%		59	%		45	%		39	%		41	%
Net assets, end of period (in thousands)	$	417,137		$	512,624		$	537,907		$	525,164		$	580,260
Ratios with no waiver of fees and assumption of expenses by
the Adviser and no reduction for fees paid indirectly:
Total expenses to average net assets		1.17	%		1.19	%		1.14	%		1.15	%		1.17	%
Net investment income (loss) to average net assets		5.17	%		4.97	%		4.87	%		4.80	%		5.09	%


*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per-share data presented above is based on the average shares outstanding for the periods presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account.
(c)	If the Fund had not recognized gains in the settlement of class action lawsuits during the year ended October 31, 2017, the total return would have been 8.94%.

The accompanying notes are an integral part of these financial statements.

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	Year			Year			Year			Year			Year
	Ended			Ended			Ended			Ended			Ended
	10/31/20			10/31/19			10/31/18			10/31/17			10/31/16*
Class C
Net asset value, beginning of period	$	9.79		$	9.57		$	10.01		$	9.63		$	9.52
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.41		$	0.40		$	0.40		$	0.41		$	0.41
Net realized and unrealized gain (loss) on investments		(0.58	)		0.25			(0.45	)		0.38			0.19
Net increase (decrease) from investment operations	$	(0.17	)	$	0.65		$	(0.05	)	$	0.79		$	0.60
Distributions to shareowners:
Net investment income	$	(0.44	)	$	(0.43	)	$	(0.39	)	$	(0.41	)	$	(0.42	)
Net realized gain		—			—			—			—			(0.07	)
Total distributions	$	(0.44	)	$	(0.43	)	$	(0.39	)	$	(0.41	)	$	(0.49	)
Net increase (decrease) in net asset value	$	(0.61	)	$	0.22		$	(0.44	)	$	0.38		$	0.11
Net asset value, end of period	$	9.18		$	9.79		$	9.57		$	10.01		$	9.63
Total return (b)		(1.71	)%		6.98	%		(0.52	)%		8.29	%(c)		6.60	%
Ratio of net expenses to average net assets		1.87	%		1.94	%		1.86	%		1.86	%		1.88	%
Ratio of net investment income (loss) to average net assets		4.48	%		4.21	%		4.10	%		4.11	%		4.40	%
Portfolio turnover rate		85	%		59	%		45	%		39	%		41	%
Net assets, end of period (in thousands)	$	17,019		$	24,166		$	37,546		$	192,558		$	259,910


*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per-share data presented above is based on the average shares outstanding for the periods presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account.
(c)	If the Fund had not recognized gains in the settlement of class action lawsuits during the year ended October 31, 2017, the total return would have been 8.18%.

The accompanying notes are an integral part of these financial statements.

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Financial Highlights (continued)


	Year			Year			Year			Year			Year
	Ended			Ended			Ended			Ended			Ended
	10/31/20			10/31/19			10/31/18			10/31/17			10/31/16*
Class R
Net asset value, beginning of period	$	10.84		$	10.61		$	11.09		$	10.68		$	10.53
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.50		$	0.48		$	0.49		$	0.48		$	0.49
Net realized and unrealized gain (loss) on investments		(0.63	)		0.27			(0.50	)		0.41			0.22
Net increase (decrease) from investment operations	$	(0.13	)	$	0.75		$	(0.01	)	$	0.89		$	0.71
Distributions to shareowners:
Net investment income	$	(0.51	)	$	(0.52	)	$	(0.47	)	$	(0.48	)	$	(0.49	)
Net realized gain		—			—			—			—			(0.07	)
Total distributions	$	(0.51	)	$	(0.52	)	$	(0.47	)	$	(0.48	)	$	(0.56	)
Net increase (decrease) in net asset value	$	(0.64	)	$	0.23		$	(0.48	)	$	0.41		$	0.15
Net asset value, end of period	$	10.20		$	10.84		$	10.61		$	11.09		$	10.68
Total return (b)		(1.08	)%		7.28	%		(0.14	)%		8.50	%(c)		7.11	%(d)
Ratio of net expenses to average net assets		1.51	%		1.63	%		1.50	%		1.56	%		1.49	%
Ratio of net investment income (loss) to average net assets		4.82	%		4.51	%		4.48	%		4.39	%		4.76	%
Portfolio turnover rate		85	%		59	%		45	%		39	%		41	%
Net assets, end of period (in thousands)	$	11,556		$	15,332		$	18,405		$	24,366		$	29,721


*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per-share data presented above is based on the average shares outstanding for the periods presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period.
(c)	If the Fund had not recognized gains in the settlement of class action lawsuits during the year ended October 31, 2017, the total return would have been 8.41%.
(d)	If the Fund had not recognized gains in the settlement of class action lawsuits during the year ended October 31, 2016, the total return would have been 7.01%.

The accompanying notes are an integral part of these financial statements.

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	Year			Year			Year			Year			Year
	Ended			Ended			Ended			Ended			Ended
	10/31/20			10/31/19			10/31/18			10/31/17			10/31/16*
Class Y
Net asset value, beginning of period	$	9.59		$	9.38		$	9.81		$	9.44		$	9.34
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.50		$	0.50		$	0.50		$	0.49		$	0.49
Net realized and unrealized gain (loss) on investments		(0.57	)		0.24			(0.45	)		0.37			0.18
Net increase (decrease) from investment operations	$	(0.07	)	$	0.74		$	0.05		$	0.86		$	0.67
Distributions to shareowners:
Net investment income	$	(0.52	)	$	(0.53	)	$	(0.48	)	$	(0.49	)	$	(0.50	)
Net realized gain		—			—			—			—			(0.07	)
Total distributions	$	(0.52	)	$	(0.53	)	$	(0.48	)	$	(0.49	)	$	(0.57	)
Net increase (decrease) in net asset value	$	(0.59	)	$	0.21		$	(0.43	)	$	0.37		$	0.10
Net asset value, end of period	$	9.00		$	9.59		$	9.38		$	9.81		$	9.44
Total return (b)		(0.62	)%		8.12	%		0.51	%		9.34	%(c)		7.62	%
Ratio of net expenses to average net assets		0.85	%		0.88	%		0.85	%		0.87	%		0.87	%
Ratio of net investment income (loss) to average net assets		5.50	%		5.27	%		5.15	%		5.08	%		5.39	%
Portfolio turnover rate		85	%		59	%		45	%		39	%		41	%
Net assets, end of period (in thousands)	$	176,362		$	200,617		$	205,543		$	229,866		$	230,343
Ratios with no waiver of fees and assumption of expenses by
the Adviser and no reduction for fees paid indirectly:
Total expenses to average net assets		0.87	%		0.88	%		0.85	%		0.87	%		0.87	%
Net investment income (loss) to average net assets		5.48	%		5.27	%		5.15	%		5.08	%		5.39	%


*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per-share data presented above is based on the average shares outstanding for the periods presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period.
(c)	If the Fund had not recognized gains in the settlement of class action lawsuits during the year ended October 31, 2017, the total return would have been 9.23%.

The accompanying notes are an integral part of these financial statements.

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Notes to Financial Statements | 10/31/20

1. Organization and Significant Accounting Policies

Pioneer High Yield Fund (the “Fund”) is a Delaware statutory Trust. The Fund is registered under the Investment Company Act of 1940 as a diversified, open-end management investment company. The investment objective of the Fund is to maximize total return through a combination of income and capital appreciation.

The Fund offers five classes of shares designated as Class A, Class C, Class K, Class R and Class Y shares. Class K shares had not commenced operations as of October 31, 2020. Each class of shares represents an interest in the same portfolio of investments of the Fund and has identical rights (based on relative net asset values) to assets and liquidation proceeds. Share classes can bear different rates of class-specific fees and expenses, such as transfer agent and distribution fees. Differences in class-specific fees and expenses will result in differences in net investment income and, therefore, the payment of different dividends from net investment income earned by each class. The Amended and Restated Declaration of Trust of the Fund gives the Board of Trustees the flexibility to specify either per-share voting or dollar-weighted voting when submitting matters for shareowner approval. Under per-share voting, each share of a class of the Fund is entitled to one vote. Under dollar-weighted voting, a shareowner’s voting power is determined not by the number of shares owned, but by the dollar value of the shares on the record date. Each share class has exclusive voting rights with respect to matters affecting only that class, including with respect to the distribution plan for that class. There is no distribution plan for Class Y shares.

Amundi Pioneer Asset Management, Inc., an indirect, wholly owned subsidiary of Amundi and Amundi's wholly owned subsidiary, Amundi USA, Inc., serves as the Fund’s investment adviser (the “Adviser”). Amundi Pioneer Distributor, Inc., an affiliate of Amundi Pioneer Asset Management, Inc., serves as the Fund’s distributor (the “Distributor”).

During March 2017, the Financial Accounting Standards Board (FASB) issued an Accounting Standard Update, ASU 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities (“ASU 2017-08”), which shortens the amortization period for purchased non-contingently callable debt securities held at a premium. ASU 2017-08 specifies that the premium amortization period ends at the earliest call date, for certain purchased non-contingently callable debt securities. ASU 2017-08 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Fund has adopted ASU 2017-08 as of January 1, 2019. The implementation of ASU 2017-08 did not have a material impact on the Fund's financial statements.

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In March 2020, FASB issued an Accounting Standard Update, ASU 2020-04, Reference Rate Reform (Topic 848) — Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”), which provides optional, temporary relief with respect to the financial reporting of contracts subject to certain types of modifications due to the planned discontinuation of the London Interbank Offered Rate (“LIBOR”) and other LIBOR-based reference rates at the end of 2021. The temporary relief provided by ASU 2020-04 is effective for certain reference rate-related contract modifications that occur during the period from March 12, 2020 through December 31, 2022. Management is evaluating the impact of ASU 2020-04 on the Fund's investments, derivatives, debt and other contracts that will undergo reference rate-related modifications as a result of the reference rate reform.

The Fund is an investment company and follows investment company accounting and reporting guidance under U.S. Generally Accepted Accounting Principles (“U.S. GAAP”). U.S. GAAP requires the management of the Fund to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of income, expenses and gain or loss on investments during the reporting period. Actual results could differ from those estimates.

The following is a summary of significant accounting policies followed by the Fund in the preparation of its financial statements:

A. Security Valuation

The net asset value of the Fund is computed once daily, on each day the New York Stock Exchange (“NYSE”) is open, as of the close of regular trading on the NYSE.

Fixed-income securities are valued by using prices supplied by independent pricing services, which consider such factors as market prices, market events, quotations from one or more brokers, Treasury spreads, yields, maturities and ratings, or may use a pricing matrix or other fair value methods or techniques to provide an estimated value of the security or instrument. A pricing matrix is a means of valuing a debt security on the basis of current market prices for other debt securities, historical trading patterns in the market for fixed-income securities and/or other factors. Non-U.S. debt securities that are listed on an exchange will be valued at the bid price obtained from an independent third party pricing service. When independent third party pricing services are unable to supply prices, or when prices or market quotations are considered to be unreliable, the value of that security may be determined using quotations from one or more broker-dealers.

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Loan interests are valued in accordance with guidelines established by the Board of Trustees at the mean between the last available bid and asked prices from one or more brokers or dealers as obtained from Loan Pricing Corporation, an independent third party pricing service. If price information is not available from Loan Pricing Corporation, or if the price information is deemed to be unreliable, price information will be obtained from an alternative loan interest pricing service. If no reliable price quotes are available from either the primary or alternative pricing service, broker quotes will be solicited.

Event-linked bonds are valued at the bid price obtained from an independent third party pricing service. Other insurance-linked securities (including reinsurance sidecars, collateralized reinsurance and industry loss warranties) may be valued at the bid price obtained from an independent pricing service, or through a third party using a pricing matrix, insurance industry valuation models, or other fair value methods or techniques to provide an estimated value of the instrument.

Equity securities that have traded on an exchange are valued by using the last sale price on the principal exchange where they are traded. Equity securities that have not traded on the date of valuation, or securities for which sale prices are not available, generally are valued using the mean between the last bid and asked prices or, if both last bid and asked prices are not available, at the last quoted bid price. Last sale and bid and asked prices are provided by independent third party pricing services. In the case of equity securities not traded on an exchange, prices are typically determined by independent third party pricing services using a variety of techniques and methods.

The value of foreign securities is translated into U.S. dollars based on foreign currency exchange rate quotations supplied by a third party pricing source. Trading in non-U.S. equity securities is substantially completed each day at various times prior to the close of the NYSE. The values of such securities used in computing the net asset value of the Fund's shares are determined as of such times. The Fund may use a fair value model developed by an independent pricing service to value non-U.S. equity securities.

Forward foreign currency exchange contracts are valued daily using the foreign exchange rate or, for longer term forward contract positions, the spot currency rate and the forward points on a daily basis, in each case provided by a third party pricing service. Contracts whose forward settlement date falls between two quoted days are valued by interpolation.

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Swap contracts, including interest rate swaps, caps and floors (other than centrally cleared swap contracts), are valued at the dealer quotations obtained from reputable International Swap Dealers Association members. Centrally cleared swaps are valued at the daily settlement price provided by the central clearing counterparty.

Repurchase agreements are valued at par. Cash may include overnight time deposits at approved financial institutions.

Securities or loan interests for which independent pricing services or broker-dealers are unable to supply prices or for which market prices and/or quotations are not readily available or are considered to be unreliable are valued by a fair valuation team comprised of certain personnel of the Adviser pursuant to procedures adopted by the Fund’s Board of Trustees. The Adviser’s fair valuation team uses fair value methods approved by the Valuation Committee of the Board of Trustees. The Adviser’s fair valuation team is responsible for monitoring developments that may impact fair valued securities and for discussing and assessing fair values on an ongoing basis, and at least quarterly, with the Valuation Committee of the Board of Trustees.

Inputs used when applying fair value methods to value a security may include credit ratings, the financial condition of the company, current market conditions and comparable securities. The Fund may use fair value methods if it is determined that a significant event has occurred after the close of the exchange or market on which the security trades and prior to the determination of the Fund’s net asset value. Examples of a significant event might include political or economic news, corporate restructurings, natural disasters, terrorist activity or trading halts. Thus, the valuation of the Fund’s securities may differ significantly from exchange prices, and such differences could be material.

At October 31, 2020, three securities were valued using fair value methods (in addition to securities valued using prices supplied by independent pricing services, broker-dealers or using a third party insurance pricing model) representing 0.03% of net assets. The value of these fair valued securities was $212,195.

B. Investment Income and Transactions

Dividend income is recorded on the ex-dividend date, except that certain dividends from foreign securities where the ex-dividend date may have passed are recorded as soon as the Fund becomes aware of the ex-dividend data in the exercise of reasonable diligence.

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Interest income, including interest on income-bearing cash accounts, is recorded on the accrual basis. Dividend and interest income are reported net of unrecoverable foreign taxes withheld at the applicable country rates and net of income accrued on defaulted securities.

Interest and dividend income payable by delivery of additional shares is reclassified as PIK (payment-in-kind) income upon receipt and is included in interest and dividend income, respectively.

Principal amounts of mortgage-backed securities are adjusted for monthly paydowns. Premiums and discounts related to certain mortgage-backed securities are amortized or accreted in proportion to the monthly paydowns. All discounts/premiums on purchase prices of debt securities are accreted/amortized for financial reporting purposes over the life of the respective securities, and such accretion/amortization is included in interest income.

Security transactions are recorded as of trade date. Gains and losses on sales of investments are calculated on the identified cost method for both financial reporting and federal income tax purposes.

C. Foreign Currency Translation

The books and records of the Fund are maintained in U.S. dollars. Amounts denominated in foreign currencies are translated into U.S. dollars using current exchange rates.

Net realized gains and losses on foreign currency transactions, if any, represent, among other things, the net realized gains and losses on foreign currency exchange contracts, disposition of foreign currencies and the difference between the amount of income accrued and the U.S. dollars actually received. Further, the effects of changes in foreign currency exchange rates on investments are not segregated on the Statement of Operations from the effects of changes in the market prices of those securities, but are included with the net realized and unrealized gain or loss on investments.

D. Federal Income Taxes

It is the Fund’s policy to comply with the requirements of the Internal Revenue Code applicable to regulated investment companies and to distribute all of its net taxable income and net realized capital gains, if any, to its shareowners. Therefore, no provision for federal income taxes is required. As of October 31, 2020, the Fund did not accrue any interest or penalties with respect to uncertain tax positions, which, if applicable, would be recorded as an income tax expense on the Statement of Operations. Tax returns filed within the prior three years remain subject to examination by federal and state tax authorities.

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The amount and character of income and capital gain distributions to shareowners are determined in accordance with federal income tax rules, which may differ from U.S. GAAP. Distributions in excess of net investment income or net realized gains are temporary over distributions for financial statement purposes resulting from differences in the recognition or classification of income or distributions for financial statement and tax purposes. Capital accounts within the financial statements are adjusted for permanent book/tax differences to reflect tax character, but are not adjusted for temporary differences.

At October 31, 2020, the Fund reclassified $6,651 to decrease distributable earnings and $6,651 to increase paid-in capital to reflect permanent book/tax differences. These adjustments have no impact on net assets or the results of operations.

At October 31, 2020, the Fund was permitted to carry forward indefinitely $16,078,423 of short-term losses and $44,451,077 of long-term losses under the Regulated Investment Company Modernization Act of 2010 without limitation.

The tax character of distributions paid during the years ended October 31, 2020 and October 31, 2019, were as follows:


	2020		2019
Distributions paid from:
Ordinary income	$	36,522,622	$	40,675,302
Total	$	36,522,622	$	40,675,302

The following shows the components of distributable earnings (losses) on a federal income tax basis at October 31, 2020:


	2020
Distributable earnings/(losses):
Undistributed ordinary income	$	534,240
Capital loss carryforward		(60,529,500	)
Dividend payable		(271,093	)
Net unrealized depreciation		(9,810,233	)
Total	$	(70,076,586	)

The difference between book basis and tax basis unrealized depreciation is attributable to the tax deferral of losses on wash sales, the mark-to-market of foreign currency exchange contracts and swaps, adjustments relating to event linked bonds and swaps.

E. Fund Shares

The Fund records sales and repurchases of its shares as of trade date. The Distributor earned $11,147 in underwriting commissions on the sale of Class A shares during the year ended October 31, 2020.

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F. Class Allocations

Income, common expenses and realized and unrealized gains and losses are calculated at the Fund level and allocated daily to each class of shares based on its respective percentage of adjusted net assets at the beginning of the day.

Distribution fees are calculated based on the average daily net asset value attributable to Class A, Class C and Class R shares of the Fund, respectively (see Note 4). Class Y shares do not pay distribution fees. All expenses and fees paid to the Fund’s transfer agent for its services are allocated among the classes of shares based on the number of accounts in each class and the ratable allocation of related out-of-pocket expenses (see Note 3).

The Fund declares as daily dividends substantially all of its net investment income. All dividends are paid on a monthly basis. Short-term capital gain distributions, if any, may be declared with the daily dividends. Distributions to shareowners are recorded as of the ex-dividend date. Distributions paid by the Fund with respect to each class of shares are calculated in the same manner and at the same time, except that net investment income dividends to Class A, Class C, Class R and Class Y shares can reflect different transfer agent and distribution expense rates.

G. Risks

The value of securities 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, the spread of infectious illness or other public health issues, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment. In the past several years, financial markets have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. These conditions may continue, recur, worsen or spread. 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.

At times, the Fund’s investments may represent industries or industry sectors that are interrelated or have common risks, making the Fund more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors. The Fund’s investments in foreign markets and countries with limited developing markets may subject the Fund to a greater degree of risk than investments in a developed market. These risks include disruptive political or economic conditions and the imposition of adverse governmental laws or currency exchange restrictions.

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The Fund invests in below-investment-grade (high-yield) debt securities and preferred stocks. Some of these high-yield securities may be convertible into equity securities of the issuer. Debt securities rated below-investment-grade are commonly referred to as “junk bonds” and are considered speculative. These securities involve greater risk of loss, are subject to greater price volatility, and are less liquid, especially during periods of economic uncertainty or change, than higher rated debt securities. The Fund’s investments, payment obligations and financing terms may be based on floating rates, such as LIBOR (London Interbank Offered Rate). Plans are underway to phase out the use of LIBOR by the end of 2021. There remains uncertainty regarding the nature of any replacement rate and the impact of the transition from LIBOR on the fund, issuers of instruments in which the fund invests, and financial markets generally.

With the increased use of technologies such as the Internet to conduct business, the Fund is susceptible to operational, information security and related risks. While the Fund’s Adviser has established business continuity plans in the event of, and risk management systems to prevent, limit or mitigate, such cyber-attacks, there are inherent limitations in such plans and systems, including the possibility that certain risks have not been identified. Furthermore, the Fund cannot control the cybersecurity plans and systems put in place by service providers to the Fund such as Brown Brothers Harriman & Co., the Fund’s custodian and accounting agent, and DST Asset Manager Solutions, Inc., the Fund’s transfer agent. In addition, many beneficial owners of Fund shares hold them through accounts at broker-dealers, retirement platforms and other financial market participants over which neither the Fund nor Amundi exercises control. Each of these may in turn rely on service providers to them, which are also subject to the risk of cyber-attacks. Cybersecurity failures or breaches at Amundi or the Fund’s service providers or intermediaries have the ability to cause disruptions and impact business operations, potentially resulting in financial losses, interference with the Fund’s ability to calculate its net asset value, impediments to trading, the inability of Fund shareowners to effect share purchases, redemptions or exchanges or receive distributions, loss of or unauthorized access to private shareowner information and violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, or additional compliance costs. Such costs and losses may not be covered under any insurance. In addition, maintaining vigilance against cyber-attacks may involve substantial costs over time, and system enhancements may themselves be subject to cyber-attacks.

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COVID-19

The respiratory illness COVID-19 caused by a novel coronavirus has resulted in a global pandemic and 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. 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. The ultimate economic fallout from the pandemic, and the long-term impact on economies, markets, industries and individual issuers, are not known. 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, and whether they will be effective to mitigate the economic and market disruption, will 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.

The Fund’s prospectus contains unaudited information regarding the Fund’s principal risks. Please refer to that document when considering the Fund’s principal risks.

H. Restricted Securities

Restricted Securities are subject to legal or contractual restrictions on resale. Restricted securities generally are resold in transactions exempt from registration under the Securities Act of 1933. Private placement securities are generally considered to be restricted except for those securities traded between qualified institutional investors under the provisions of Rule 144A of the Securities Act of 1933.

Disposal of restricted investments may involve negotiations and expenses, and prompt sale at an acceptable price may be difficult to achieve. Restricted investments held by the Fund at October 31, 2020 are listed in the Schedule of Investments.

I. Insurance-Linked Securities (“ILS”)

The Fund invests in ILS. The Fund could lose a portion or all of the principal it has invested in an ILS, and the right to additional interest or dividend payments with respect to the security, upon the occurrence of one or more trigger events, as defined within the terms of an insurance-linked security.

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Trigger events, generally, are hurricanes, earthquakes, or other natural events of a specific size or magnitude that occur in a designated geographic region during a specified time period, and/or that involve losses or other metrics that exceed a specific amount. There is no way to accurately predict whether a trigger event will occur, and accordingly, ILS carry significant risk. The Fund is entitled to receive principal, and interest and/or dividend payments so long as no trigger event occurs of the description and magnitude specified by the instrument. In addition to the specified trigger events, ILS may expose the Fund to other risks, including but not limited to issuer (credit) default, adverse regulatory or jurisdictional interpretations and adverse tax consequences.

The Fund’s investments in ILS may include event-linked bonds. ILS also may include special purpose vehicles (“SPVs”) or similar instruments structured to comprise a portion of a reinsurer’s catastrophe-oriented business, known as quota share instruments (sometimes referred to as reinsurance sidecars), or to provide reinsurance relating to specific risks to insurance or reinsurance companies through a collateralized instrument, known as collateralized reinsurance. Structured reinsurance investments also may include industry loss warranties (“ILWs”). A traditional ILW takes the form of a bilateral reinsurance contract, but there are also products that take the form of derivatives, collateralized structures, or exchange-traded instruments.

Where the ILS are based on the performance of underlying reinsurance contracts, the Fund has limited transparency into the individual underlying contracts, and therefore must rely upon the risk assessment and sound underwriting practices of the issuer. Accordingly, it may be more difficult for the Adviser to fully evaluate the underlying risk profile of the Fund’s structured reinsurance investments, and therefore the Fund’s assets are placed at greater risk of loss than if the Adviser had more complete information. Structured reinsurance instruments generally will be considered illiquid securities by the Fund. These securities may be difficult to purchase, sell or unwind. Illiquid securities also may be difficult to value. If the Fund is forced to sell an illiquid asset, the Fund may be forced to sell at a loss.

J. Repurchase Agreements

Repurchase agreements are arrangements under which the Fund purchases securities from a broker-dealer or a bank, called the counterparty, upon the agreement of the counterparty to repurchase the securities from the Fund at a later date, and at a specific price, which is typically higher than the purchase price paid by the Fund. The securities purchased serve as the Fund’s collateral for the obligation of the counterparty to repurchase the

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securities. The value of the collateral, including accrued interest, is required to be equal to or in excess of the repurchase price. The collateral for all repurchase agreements is held in safekeeping in the customer-only account of the Fund’s custodian or a sub-custodian of the Fund. The Adviser is responsible for determining that the value of the collateral remains at least equal to the repurchase price. In the event of a default by the counterparty, the Fund is entitled to sell the securities, but the Fund may not be able to sell them for the price at which they were purchased, thus causing a loss to the Fund. Additionally, if the counterparty becomes insolvent, there is some risk that the Fund will not have a right to the securities, or the immediate right to sell the securities.

As of and for the year ended October 31, 2020, the Fund had no open repurchase agreements.

K. Forward Foreign Currency Exchange Contracts

The Fund may enter into forward foreign currency exchange contracts (“contracts”) for the purchase or sale of a specific foreign currency at a fixed price on a future date. All contracts are marked-to-market daily at the applicable exchange rates, and any resulting unrealized appreciation or depreciation is recorded in the Fund’s financial statements. The Fund records realized gains and losses at the time a contract is offset by entry into a closing transaction or extinguished by delivery of the currency. Risks may arise upon entering into these contracts from the potential inability of counterparties to meet the terms of the contract and from unanticipated movements in the value of foreign currencies relative to the U.S. dollar (see Note 7).

During the year ended October 31, 2020, the Fund had entered into various forward foreign currency exchange contracts that obligated the Fund to deliver or take delivery of currencies at specified future maturity dates. Alternatively, prior to the settlement date of a forward foreign currency exchange contract, the Fund may close out such contract by entering into an offsetting contract.

The average market value of forward foreign currency exchange contracts open during the year ended October 31, 2020, was $(692,096). Open forward foreign currency exchange contracts outstanding at October 31, 2020, are listed in the Schedule of Investments.

L. Credit Default Swap Contracts

A credit default swap is a contract between a buyer of protection and a seller of protection against a pre-defined credit event or an underlying reference obligation, which may be a single security or a basket or index of securities. The Fund may buy or sell credit default swap contracts to seek

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to increase the Fund’s income, or to attempt to hedge the risk of default on portfolio securities. A credit default swap index is used to hedge risk or take a position on a basket of credit entities or indices.

As a seller of protection, the Fund would be required to pay the notional (or other agreed-upon) value of the referenced debt obligation to the counterparty in the event of a default by a U.S. or foreign corporate issuer of a debt obligation, which would likely result in a loss to the Fund. In return, the Fund would receive from the counterparty a periodic stream of payments during the term of the contract, provided that no event of default occurred. The maximum exposure of loss to the seller would be the notional value of the credit default swaps outstanding. If no default occurs, the Fund would keep the stream of payments and would have no payment obligation. The Fund may also buy credit default swap contracts in order to hedge against the risk of default of debt securities, in which case the Fund would function as the counterparty referenced above.

As a buyer of protection, the Fund makes an upfront or periodic payment to the protection seller in exchange for the right to receive a contingent payment. An upfront payment made by the Fund, as the protection buyer, is recorded within the “Swap contracts, at value” line item on the Statement of Assets and Liabilities. Periodic payments received or paid by the Fund are recorded as realized gains or losses on the Statement of Operations.

Credit default swap contracts are marked-to-market daily using valuations supplied by independent sources, and the change in value, if any, is recorded within the “Swap contracts, at value” line item on the Statement of Assets and Liabilities. Payments received or made as a result of a credit event or upon termination of the contract are recognized, net of the appropriate amount of the upfront payment, as realized gains or losses on the Statement of Operations.

Credit default swap contracts involving the sale of protection may involve greater risks than if the Fund had invested in the referenced debt instrument directly. Credit default swap contracts are subject to general market risk, liquidity risk, counterparty risk and credit risk. If the Fund is a protection buyer and no credit event occurs, it will lose its investment. If the Fund is a protection seller and a credit event occurs, the value of the referenced debt instrument received by the Fund, together with the periodic payments received, may be less than the amount the Fund pays to the protection buyer, resulting in a loss to the Fund. In addition, obligations under sell protection credit default swaps may be partially offset by net amounts received from settlement of buy protection credit default swaps entered into by the Fund for the same reference obligation with the same counterparty.

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Certain swap contracts that are cleared through a central clearinghouse are referred to as centrally cleared swaps. All payments made or received by the Fund are pursuant to a centrally cleared swap contract with the central clearing party rather than the original counterparty. Upon entering into a centrally cleared swap contract, the Fund is required to make an initial margin deposit, either in cash or in securities. The daily change in value on open centrally cleared contracts is recorded as “Variation margin for centrally cleared swap contracts” on the Statement of Assets and Liabilities. Cash received from or paid to the broker related to previous margin movement is held in a segregated account at the broker and is recorded as either “Due from broker for swaps” or “Due to broker for swaps” on the Statement of Assets and Liabilities. The amount of cash deposited with a broker as collateral at October 31, 2020, is recorded as “Swaps collateral” on the Statement of Assets and Liabilities.

The average market value of credit default swap contracts open during the year ended October 31, 2020, was $(454,360). Open credit default swap contracts at October 31, 2020, are listed in the Schedule of Investments.

2. Management Agreement

The Adviser manages the Fund’s portfolio. Management fees are calculated daily and paid monthly at the annual rate of 0.70% of the Fund’s average daily net assets up to $500 million, 0.65% of the Fund’s average daily net assets on the next $500 million, 0.60% of the Fund’s average daily net assets on the next $4 billion, 0.55% of the Fund’s average daily net assets on the next $1 billion, 0.50% of the Fund’s average daily net assets on the next $1 billion, 0.45% of the Fund’s average daily net assets on the next $1 billion, 0.40% of the Fund’s average daily net assets on the next $1 billion, 0.35% of the Fund’s average daily net assets on the next $1 billion, and 0.30% of the Fund’s average daily net assets on assets over $10 billion. For the year ended October 31, 2020, the effective management fee (excluding waivers and/or assumption of expenses) was equivalent to 0.69% of the Fund’s average daily net assets.

The Adviser has contractually agreed to limit ordinary operating expenses (ordinary operating expenses means all fund expenses other than extraordinary expenses, such as litigation, taxes, brokerage commissions and acquired fund fees and expenses) of the Fund to the extent required to reduce Fund expenses to 1.10% and 0.85% of the average daily net assets attributable to Class A and Class Y shares, respectively. These expense limitations are in effect through March 1, 2021. There can be no assurance that the Adviser will extend the expense limitation agreement for a class of

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shares beyond the date referred to above. Fees waived and expenses reimbursed during the year ended October 31, 2020 are reflected on the Statement of Operations.

In addition, under the management and administration agreements, certain other services and costs, including accounting, regulatory reporting and insurance premiums, are paid by the Fund as administrative reimbursements. Included in “Due to affiliates” reflected on the Statement of Assets and Liabilities is $45,485 in management fees, administrative costs and certain other reimbursements payable to the Adviser at October 31, 2020.

3. Transfer Agent

DST Asset Manager Solutions, Inc. serves as the transfer agent to the Fund at negotiated rates. Transfer agent fees and payables shown on the Statement of Operations and the Statement of Assets and Liabilities, respectively, include sub-transfer agent expenses incurred through the Fund’s omnibus relationship contracts.

In addition, the Fund reimbursed the transfer agent for out-of-pocket expenses incurred by the transfer agent related to shareowner communications activities such as proxy and statement mailings, and outgoing phone calls. For the year ended October 31, 2020, such out-of-pocket expenses by class of shares were as follows:


Shareowner Communications:
Class A	$	80,018
Class C		5,627
Class R		1,639
Class Y		9,303
Total	$	96,587

4. Distribution and Service Plans

The Fund has adopted a distribution plan (the “Plan”) pursuant to Rule 12b-1 of the Investment Company Act of 1940 with respect to its Class A, Class C and Class R shares. Pursuant to the Plan, the Fund pays the Distributor 0.25% of the average daily net assets attributable to Class A shares as compensation for personal services and/or account maintenance services or distribution services with regard to Class A shares. Pursuant to the Plan, the Fund also pays the Distributor 1.00% of the average daily net assets attributable to Class C shares. The fee for Class C shares consists of a 0.25% service fee and a 0.75% distribution fee paid as compensation for personal services and/or account maintenance services or distribution services with regard to Class C shares. Pursuant to the Plan, the Fund further pays the Distributor 0.50% of the average daily net assets attributable to Class R

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shares for distribution services. Included in “Due to affiliates” reflected on the Statement of Assets and Liabilities is $57,532 in distribution fees payable to the Distributor at October 31, 2020.

The Fund also has adopted a separate service plan for Class R shares (the “Service Plan”). The Service Plan authorizes the Fund to pay securities dealers, plan administrators or other service organizations that agree to provide certain services to retirement plans or plan participants holding shares of the Fund a service fee of up to 0.25% of the Fund’s average daily net assets attributable to Class R shares held by such plans.

In addition, redemptions of Class A and Class C shares may be subject to a contingent deferred sales charge (“CDSC”). A CDSC of 1.00% may be imposed on redemptions of certain net asset value purchases of Class A shares within 12 months of purchase. Redemptions of Class C shares within 12 months of purchase are subject to a CDSC of 1.00% based on the lower of cost or market value of shares being redeemed. Shares purchased as part of an exchange remain subject to any CDSC that applied to the original purchase of those shares. There is no CDSC for Class R or Class Y shares. Proceeds from the CDSCs are paid to the Distributor. For the year ended October 31, 2020, CDSCs in the amount of $2,041 were paid to the Distributor.

5. Line of Credit Facility

The Fund, along with certain other funds in the Pioneer Family of Funds (the “Funds”), participates in a committed, unsecured revolving line of credit (“credit facility”). Borrowings are used solely for temporary or emergency purposes. The Fund may borrow up to the lesser of the amount available under the credit facility or the limits set for borrowing by the Fund’s prospectus and the 1940 Act. Effective March 11, 2020, the Fund participates in a facility in the amount of $300 million. Prior to March 11, 2020, the Fund participated in a facility in the amount of $250 million. Under such facility, depending on the type of loan, interest on borrowings is payable at the London Interbank Offered Rate (“LIBOR”) plus a credit spread. The Fund also pays an annual commitment fee in the amount of 0.30% of the daily unused portion of each lender’s commitment to participate in the credit facility. The commitment fee is allocated among participating Funds based on an allocation schedule set forth in the credit agreement. For the year ended October 31, 2020, the Fund had no borrowings under the credit facility.

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6. Master Netting Agreements

The Fund has entered into an International Swaps and Derivatives Association, Inc. Master Agreement (“ISDA Master Agreement”) or similar agreement with substantially of all its derivative counterparties. An ISDA Master Agreement is a bilateral agreement between the Fund and a counterparty that governs the trading of certain Over the Counter (“OTC”) derivatives and typically contains, among other things, close-out and set-off provisions which apply upon the occurrence of an event of default and/or a termination event as defined under the relevant ISDA Master Agreement. The ISDA Master Agreement may also give a party the right to terminate all transactions traded under such agreement if, among other things, there is deterioration in the credit quality of the other party.

Upon an event of default or a termination of the ISDA Master Agreement, the non-defaulting party has the right to close-out all transactions under such agreement and to net amounts owed under each transaction to determine one net amount payable by one party to the other. The right to close out and net payments across all transactions under the ISDA Master Agreement could result in a reduction of the Fund’s credit risk to its counterparty equal to any amounts payable by the Fund under the applicable transactions, if any. However, the Fund’s right to set-off may be restricted or prohibited by the bankruptcy or insolvency laws of the particular jurisdiction to which each specific ISDA Master Agreement of each counterparty is subject.

The collateral requirements for derivatives transactions under an ISDA Master Agreement are governed by a credit support annex to the ISDA Master Agreement. Collateral requirements are generally determined at the close of business each day and are typically based on changes in market values for each transaction under an ISDA Master Agreement and netted into one amount for such agreement. Generally, the amount of collateral due from or to a counterparty is subject to threshold (a “minimum transfer amount”) before a transfer is required, which may vary by counterparty. Collateral pledged for the benefit of the Fund and/or counterparty is held in segregated accounts by the Fund’s custodian and cannot be sold, re-pledged, assigned or otherwise used while pledged. Cash that has been segregated to cover the Fund’s collateral obligations, if any, will be reported separately on the Statement of Assets and Liabilities as “Swaps collateral”. Securities pledged by the Fund as collateral, if any, are identified as such in the Schedule of Investments.

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Financial instruments subject to an enforceable master netting agreement, such as an ISDA Master Agreement, have been offset on the Statement of Assets and Liabilities. The following charts show gross assets and liabilities of the Fund as of October 31, 2020.


	Derivative
	Assets
	Subject to	Derivatives	Non-Cash	Cash	Net Amount
	Master Netting	Available	Collateral	Collateral	of Derivative
Counterparty	Agreement	for Offset	Received (a)	Received (a)	Assets (b)
JPMorgan Chase
Bank NA	$6,716	$ —	$ —	$ —	$6,716
Total	$6,716	$ —	$ —	$ —	$6,716


	Derivative
	Liabilities
	Subject to	Derivatives	Non-Cash	Cash	Net Amount
	Master Netting	Available	Collateral	Collateral	of Derivative
Counterparty	Agreement	for Offset	Pledged (a)	Pledged (a)	Liabilities (c)
JPMorgan Chase
Bank NA	$ —	$ —	$ —	$ —	$ —
Total	$ —	$ —	$ —	$ —	$ —

(a) The amount presented here may be less than the total amount of collateral received/pledged as the net amount of derivative assets and liabilities cannot be less than $0.

(b) Represents the net amount due from the counterparty in the event of default.

7. Additional Disclosures about Derivative Instruments and Hedging Activities

The Fund’s use of derivatives may enhance or mitigate the Fund’s exposure to the following risks:

Interest rate risk relates to the fluctuations in the value of interest-bearing securities due to changes in the prevailing levels of market interest rates.

Credit risk relates to the ability of the issuer of a financial instrument to make further principal or interest payments on an obligation or commitment that it has to the Fund.

Foreign exchange rate risk relates to fluctuations in the value of an asset or liability due to changes in currency exchange rates.

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Equity risk relates to the fluctuations in the value of financial instruments as a result of changes in market prices (other than those arising from interest rate risk or foreign exchange rate risk), whether caused by factors specific to an individual investment, its issuer, or all factors affecting all instruments traded in a market or market segment.

Commodity risk relates to the risk that the value of a commodity or commodity index will fluctuate based on increases or decreases in the commodities market and factors specific to a particular industry or commodity.

The fair value of open derivative instruments (not considered to be hedging instruments for accounting disclosure purposes) by risk exposure at October 31, 2020, was as follows:


Statement of Assets and Liabilities
					Foreign
	Interest		Credit		Exchange		Equity		Commodity
	Rate Risk		Risk		Rate Risk		Risk		Risk
Assets
Forward foreign currency
exchange contracts	$	—	$	—	$	6,716	$	—	$	—
Swap contracts, at value		—		815,111		—		—		—
Total Value	$	—	$	815,111	$	6,716	$	—	$	—

The effect of derivative instruments (not considered to be hedging instruments for accounting disclosure purposes) on the Statement of Operations by risk exposure at October 31, 2020, was as follows:


Statement of Operations

						Foreign
	Interest		Credit			Exchange		Equity		Commodity
	Rate Risk		Risk			Rate Risk		Risk		Risk
Net realized gain (loss) on:
Forward foreign currency
exchange contracts	$	—	$	—		$	13,428	$	—	$	—
Swap contracts		—		(2,801,079	)		—		—		—
Total Value	$	—	$	(2,801,079	)	$	13,428	$	—	$	—
Change in net unrealized
appreciation
(depreciation) on:
Forward foreign currency
exchange contracts	$	—	$	—		$	34,824	$	—	$	—
Swap contracts		—		(199,628	)		—		—		—
Total Value	$	—	$	(199,628	)	$	34,824	$	—	$	—

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8. Unfunded Loan Commitments

The Fund may enter into unfunded loan commitments. Unfunded loan commitments may be partially or wholly unfunded. During the contractual year, the Fund is obliged to provide funding to the borrower upon demand. A fee is earned by the Fund on the unfunded loan commitment and is recorded as interest income on the Statement of Operations. Unfunded loan commitments are fair valued in accordance with the valuation policy described in Footnote 1A and unrealized appreciation or depreciation, if any, is recorded on the Statement of Assets and Liabilities.

As of October 31, 2020, the Fund had the following unfunded loan commitments outstanding:


							Unrealized
							Appreciation
Loan	Principal		Cost		Value		(Depreciation)
Grupo Aeromexico, DIP Tranche 2
Term Loan	$	556,563	$	550,997	$	556,563	$	5,566
Grupo Aeromexico, Senior Secured
Tranche 1		1,005,000		995,595		994,950		(645	)
Spectacle Gary Holdings LLC		256,914		250,440		243,586		(6,854	)
Total Value	$	1,818,477	$	1,797,032	$	1,795,099	$	(1,933	)

9. Subsequent Event

On November 19, 2020, Amundi Pioneer Asset Management announced it will be rebranding the US business of Amundi as Amundi US effective January 1, 2021. The new brand identity will replace Amundi Pioneer, which was first adopted in July 2017 following the acquisition of Pioneer Investments by Amundi. In connection with these changes, Amundi Pioneer Asset Management. Inc., the investment adviser to the Pioneer funds, will change its name to Amundi Asset Management US, Inc. In addition, Amundi Pioneer Distributor, Inc., the Pioneer funds’ distributor, will change its name to Amundi Distributor US, Inc. The names of the Pioneer funds will not change in connection with this rebranding.

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Report of Independent Registered Public
Accounting Firm

To the Board of Trustees and the Shareholders of
Pioneer High Yield Fund:

Opinion on the Financial Statements

We have audited the accompanying statement of assets and liabilities of Pioneer High Yield Fund (the “Fund”), including the schedule of investments, as of October 31, 2020, and the related statement of operations for the year then ended, the statements of changes in net assets for each of the two years in the period then ended, the financial highlights for each of the four years in the period then ended and the related notes (collectively referred to as the “financial statements”). The financial highlights for the period ended October 31, 2016 were audited by another independent registered public accounting firm whose report, dated December 23, 2016, expressed an unqualified opinion on those financial highlights. In our opinion, the financial statements present fairly, in all material respects, the financial position of the Fund at October 31, 2020, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period then ended, and its financial highlights for each of the four years in the period then ended, in conformity with U.S. generally accepted accounting principles.

Basis for Opinion

These financial statements are the responsibility of the Fund’s management. Our responsibility is to express an opinion on the Fund’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (“PCAOB”) and are required to be independent with respect to the Fund in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Fund is not required to have, nor were we engaged to perform, an audit of the Fund’s internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting, but not for the purpose of expressing an opinion on the effectiveness of the Fund’s internal control over financial reporting. Accordingly, we express no such opinion.

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Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our procedures included confirmation of securities owned as of October 31, 2020, by correspondence with the custodian and brokers or by other appropriate auditing procedures where replies from brokers were not received. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

We have served as the auditor of one or more Amundi Pioneer investment companies since 2017.

Boston, Massachusetts
December 18, 2020

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Additional Information (unaudited)

The percentages of the Fund’s ordinary income distributions that are exempt from nonresident alien (NRA) tax withholding resulting from qualified interest income was 75.86%.

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Statement Regarding Liquidity Risk Management Program

As required by law, the Fund has adopted and implemented a liquidity risk management program (the “Program”) that is designed to assess and manage liquidity risk. Liquidity risk is the risk that the Fund could not meet requests to redeem its shares without significant dilution of remaining investors’ interests in the Fund. The Fund’s Board of Trustees designated a liquidity risk management committee (the “Committee”) consisting of employees of Amundi Pioneer Asset Management, Inc. (the “Adviser”) to administer the Program.

The Committee provided the Board of Trustees with a report that addressed the operation of the Program and assessed its adequacy and effectiveness of implementation (the “Report”). The Report covered the period from December 1, 2018 through March 31, 2020 (the “Reporting Period”).

The Report confirmed that, throughout the Reporting Period, the Committee had monitored the Fund’s portfolio liquidity and liquidity risk on an ongoing basis, as described in the Program and in Board reporting throughout the Reporting Period.

The Report discussed the Committee’s annual review of the Program, which addressed, among other things, the following elements of the Program:

The Committee reviewed the Fund’s investment strategy and liquidity of portfolio investments during both normal and reasonably foreseeable stressed conditions. The Committee noted that the Fund’s investment strategy continues to be appropriate for an open-end fund, taking into account, among other things, whether and to what extent the Fund held less liquid and illiquid assets and the extent to which any such investments affected the Fund’s ability to meet redemption requests. In managing and reviewing the Fund’s liquidity risk, the Committee also considered the extent to which the Fund’s investment strategy involves a relatively concentrated portfolio or large positions in particular issuers, the extent to which the Fund uses borrowing for investment purposes, and the extent to which the Fund uses derivatives (including for hedging purposes). The Committee also reviewed the Fund’s short-term and long-term cash flow projections during both normal and reasonably foreseeable stressed conditions. In assessing the Fund’s cash flow projections, the Committee considered, among other factors, historical net redemption activity, redemption policies, ownership concentration, distribution channels, and the degree of certainty associated with the Fund’s short-term and long-

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term cash flow projections. The Committee also considered the Fund’s holdings of cash and cash equivalents, as well as borrowing arrangements and other funding sources, including, if applicable, the Fund’s participation in a credit facility, as components of the Fund’s ability to meet redemption requests. The Fund has adopted an in-kind redemption policy which may be utilized to meet larger redemption requests.

The Committee reviewed the Program’s liquidity classification methodology for categorizing the Fund’s investments into one of four liquidity buckets. In reviewing the Fund’s investments, the Committee considered, among other factors, whether trading varying portions of a position in a particular portfolio investment or asset class in sizes the Fund would reasonably anticipate trading, would be reasonably expected to significantly affect liquidity.

The Committee performed an analysis to determine whether the Fund is required to maintain a Highly Liquid Investment Minimum, and determined that no such minimum is required because the Fund primarily holds highly liquid investments.

The Report stated that the Committee concluded the Program operates adequately and effectively, in all material respects, to assess and manage the Fund’s liquidity risk throughout the Reporting Period.

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Approval of Investment Management Agreement

Amundi Pioneer Asset Management, Inc. (“APAM”) serves as the investment adviser to Pioneer High Yield Fund (the “Fund”) pursuant to an investment management agreement between APAM and the Fund. In order for APAM to remain the investment adviser of the Fund, the Trustees of the Fund must determine annually whether to renew the investment management agreement for the Fund.

The contract review process began in January 2020 as the Trustees of the Fund agreed on, among other things, an overall approach and timeline for the process. Contract review materials were provided to the Trustees in March 2020, July 2020 and September 2020. In addition, the Trustees reviewed and discussed the Fund’s performance at regularly scheduled meetings throughout the year, and took into account other information related to the Fund provided to the Trustees at regularly scheduled meetings, in connection with the review of the Fund’s investment management agreement.

In March 2020, the Trustees, among other things, discussed the memorandum provided by Fund counsel that summarized the legal standards and other considerations that are relevant to the Trustees in their deliberations regarding the renewal of the investment management agreement, and reviewed and discussed the qualifications of the investment management teams for the Fund, as well as the level of investment by the Fund’s portfolio managers in the Fund. In July 2020, the Trustees, among other things, reviewed the Fund’s management fees and total expense ratios, the financial statements of APAM and its parent companies, profitability analyses provided by APAM, and analyses from APAM as to possible economies of scale. The Trustees also reviewed the profitability of the institutional business of APAM and APAM’s affiliate, Amundi Pioneer Institutional Asset Management, Inc. (“APIAM” and, together with APAM, “Amundi Pioneer”), as compared to that of APAM’s fund management business, and considered the differences between the fees and expenses of the Fund and the fees and expenses of APAM’s and APIAM’s institutional accounts, as well as the different services provided by APAM to the Fund and by APAM and APIAM to the institutional accounts. The Trustees further considered contract review materials, including additional materials received in response to the Trustees’ request, in September 2020.

At a meeting held on September 15, 2020, based on their evaluation of the information provided by APAM and third parties, the Trustees of the Fund, including the Independent Trustees voting separately, unanimously approved the renewal of the investment management agreement for another

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year. In approving the renewal of the investment management agreement, the Trustees considered various factors that they determined were relevant, including the factors described below. The Trustees did not identify any single factor as the controlling factor in determining to approve the renewal of the agreement.

Nature, Extent and Quality of Services

The Trustees considered the nature, extent and quality of the services that had been provided by APAM to the Fund, taking into account the investment objective and strategy of the Fund. The Trustees also reviewed APAM’s investment approach for the Fund and its research process. The Trustees considered the resources of APAM and the personnel of APAM who provide investment management services to the Fund. They also reviewed the amount of non-Fund assets managed by the portfolio managers of the Fund. They considered the non-investment resources and personnel of APAM that are involved in APAM’s services to the Fund, including APAM’s compliance, risk management, and legal resources and personnel. The Trustees noted the substantial attention and high priority given by APAM’s senior management to the Pioneer Fund complex. The Trustees considered the implementation and effectiveness of APAM’s business continuity plan in response to the COVID-19 pandemic.

The Trustees considered that APAM supervises and monitors the performance of the Fund’s service providers and provides the Fund with personnel (including Fund officers) and other resources that are necessary for the Fund’s business management and operations. The Trustees also considered that, as administrator, APAM is responsible for the administration of the Fund’s business and other affairs. The Trustees considered the fees paid to APAM for the provision of administration services.

Based on these considerations, the Trustees concluded that the nature, extent and quality of services that had been provided by APAM to the Fund were satisfactory and consistent with the terms of the investment management agreement.

Performance of the Fund

In considering the Fund’s performance, the Trustees regularly review and discuss throughout the year data prepared by APAM and information comparing the Fund’s performance with the performance of its peer group of funds, as classified by Morningstar, Inc. (Morningstar), and with the performance of the Fund’s benchmark index. They also discuss the Fund’s

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performance with APAM on a regular basis. The Trustees’ regular reviews and discussions were factored into the Trustees’ deliberations concerning the renewal of the investment management agreement.

Management Fee and Expenses

The Trustees considered information showing the fees and expenses of the Fund in comparison to the management fees of its peer group of funds as classified by Morningstar and also to the expense ratios of a peer group of funds selected on the basis of criteria determined by the Independent Trustees for this purpose using data provided by Strategic Insight Mutual Fund Research and Consulting, LLC (Strategic Insight), an independent third party. The peer group comparisons referred to below are organized in quintiles. Each quintile represents one-fifth of the peer group. In all peer group comparisons referred to below, first quintile is most favorable to the Fund’s shareowners. The Trustees noted that they separately review and consider the impact of the Fund’s transfer agency and Fund- and APAM-paid expenses for sub-transfer agency and intermediary arrangements, and that the results of the most recent such review were considered in the consideration of the Fund’s expense ratio.

The Trustees considered that the Fund’s management fee for the most recent fiscal year was in the fourth quintile relative to the management fees paid by other funds in its Morningstar category for the comparable period. The Trustees also considered the breakpoints in the management fee schedule and the reduced fee rates above certain asset levels. The Trustees noted the resource commitment necessary to manage a high yield fund that invests more significantly in convertible securities and invests across a broader group of sectors than a traditional high yield fund. The Trustees considered that the expense ratio of the Fund’s Class A shares for the most recent fiscal year was in the fifth quintile relative to its Strategic Insight peer group for the comparable period. The Trustees noted that APAM had agreed to waive fees and/or reimburse expenses in order to limit the ordinary operating expenses of the Fund.

The Trustees reviewed management fees charged by APAM and APIAM to institutional and other clients, including publicly offered European funds sponsored by APAM’s affiliates, unaffiliated U.S. registered investment companies (in a sub-advisory capacity), and unaffiliated foreign and domestic separate accounts. The Trustees also considered APAM’s costs in providing services to the Fund and APAM’s and APIAM’s costs in providing services to the other clients and considered the differences in management fees and profit margins for fund and non-fund services. In evaluating the fees associated with APAM’s and APIAM’s client accounts, the Trustees took into account the respective demands, resources and complexity

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associated with the Fund and other client accounts. The Trustees noted that, in some instances, the fee rates for those clients were lower than the management fee for the Fund and considered that, under the investment management agreement with the Fund, APAM performs additional services for the Fund that it does not provide to those other clients or services that are broader in scope, including oversight of the Fund’s other service providers and activities related to compliance and the extensive regulatory and tax regimes to which the Fund is subject. The Trustees also considered the entrepreneurial risks associated with APAM’s management of the Fund.

The Trustees concluded that the management fee payable by the Fund to APAM was reasonable in relation to the nature and quality of the services provided by APAM.

Profitability

The Trustees considered information provided by APAM regarding the profitability of APAM with respect to the advisory services provided by APAM to the Fund, including the methodology used by APAM in allocating certain of its costs to the management of the Fund. The Trustees also considered APAM’s profit margin in connection with the overall operation of the Fund. They further reviewed the financial results, including the profit margins, realized by APAM and APIAM from non-fund businesses. The Trustees considered APAM’s profit margins in comparison to the limited industry data available and noted that the profitability of any adviser was affected by numerous factors, including its organizational structure and method for allocating expenses. The Trustees concluded that APAM’s profitability with respect to the management of the Fund was not unreasonable.

Economies of Scale

The Trustees considered APAM’s views relating to economies of scale in connection with the Pioneer Funds as fund assets grow and the extent to which any such economies of scale are shared with the Fund and Fund shareholders. The Trustees noted the breakpoints in the management fee schedule. The Trustees recognize that economies of scale are difficult to identify and quantify, and that, among other factors that may be relevant, are the following: fee levels, expense subsidization, investment by APAM in research and analytical capabilities and APAM’s commitment and resource allocation to the Fund. The Trustees noted that profitability also may be an indicator of the availability of any economies of scale, although profitability may vary for other reasons including due to reductions in expenses. The Trustees concluded that economies of scale, if any, were being appropriately shared with the Fund.

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Other Benefits

The Trustees considered the other benefits that APAM enjoys from its relationship with the Fund. The Trustees considered the character and amount of fees paid or to be paid by the Fund, other than under the investment management agreement, for services provided by APAM and its affiliates. The Trustees further considered the revenues and profitability of APAM’s businesses other than the Fund business. To the extent applicable, the Trustees also considered the benefits to the Fund and to APAM and its affiliates from the use of “soft” commission dollars generated by the Fund to pay for research and brokerage services.

The Trustees considered that Amundi Pioneer is the principal U.S. asset management business of Amundi, which is one of the largest asset managers globally. Amundi’s worldwide asset management business manages over $1.7 trillion in assets (including the Pioneer Funds). The Trustees considered that APAM’s relationship with Amundi creates potential opportunities for APAM, APIAM and Amundi that derive from APAM’s relationships with the Fund, including Amundi’s ability to market the services of APAM globally. The Trustees noted that APAM has access to additional research and portfolio management capabilities as a result of its relationship with Amundi and Amundi’s enhanced global presence that may contribute to an increase in the resources available to APAM. The Trustees considered that APAM and the Fund receive reciprocal intangible benefits from the relationship, including mutual brand recognition and, for the Fund, direct and indirect access to the resources of a large global asset manager. The Trustees concluded that any such benefits received by APAM as a result of its relationship with the Fund were reasonable.

Conclusion

After consideration of the factors described above as well as other factors, the Trustees, including the Independent Trustees, concluded that the investment management agreement for the Fund, including the fees payable thereunder, was fair and reasonable and voted to approve the proposed renewal of the investment management agreement.

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Trustees, Officers and Service Providers

Investment Adviser and Administrator

Amundi Pioneer Asset Management, Inc.

Custodian and Sub-Administrator

Brown Brothers Harriman & Co.

Independent Registered Public Accounting Firm

Ernst & Young LLP

Principal Underwriter

Amundi Pioneer Distributor, Inc.

Legal Counsel

Morgan, Lewis & Bockius LLP

Transfer Agent

DST Asset Manager Solutions, Inc.

Proxy Voting Policies and Procedures of the Fund are available without charge, upon request, by calling our toll free number (1-800-225-6292). Information regarding how the Fund voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is publicly available to shareowners at www.amundipioneer.com/us. This information is also available on the Securities and Exchange Commission’s web site at www.sec.gov.

Trustees and Officers

The Fund’s Trustees and officers are listed below, together with their principal occupations and other directorships they have held during at least the past five years. Trustees who are interested persons of the Fund within the meaning of the 1940 Act are referred to as Interested Trustees. Trustees who are not interested persons of the Fund are referred to as Independent Trustees. Each of the Trustees serves as a Trustee of each of the 45 U.S. registered investment portfolios for which Amundi serves as investment adviser (the “Pioneer Funds”). The address for all Trustees and all officers of the Fund is 60 State Street, Boston, Massachusetts 02109.

The Statement of Additional Information of the Fund includes additional information about the Trustees and is available, without charge, upon request, by calling 1-800-225-6292.

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Independent Trustees


Name, Age and Position	Term of Office and		Other Directorships
Held With the Fund	Length of Service	Principal Occupation	Held by Trustee
Thomas J. Perna (70)	Trustee since 2006.	Private investor (2004 – 2008 and 2013 – present); Chairman (2008 – 2013)	Director, Broadridge Financial
Chairman of the Board	Serves until a successor	and Chief Executive Officer (2008 – 2012), Quadriserv, Inc. (technology	Solutions, Inc. (investor
and Trustee	trustee is elected or	products for securities lending industry); and Senior Executive Vice	communications and securities
	earlier retirement	President, The Bank of New York (financial and securities services)	processing provider for financial
	or removal.	(1986 – 2004)	services industry) (2009 – present);
			Director, Quadriserv, Inc. (2005 –
			2013); and Commissioner, New
			Jersey State Civil Service
			Commission (2011 – 2015)
John E.	Trustee since 2019.	Of Counsel (2019 – present), Partner (1983-2018), Sullivan &	Chairman, The Lakeville Journal
Baumgardner, Jr. (69)	Serves until a successor	Cromwell LLP (law firm).	Company, LLC, (privately-held
Trustee	trustee is elected or		community newspaper group)
	earlier retirement		(2015-present)
	or removal.
Diane Durnin (63)	Trustee since 2019.	Managing Director - Head of Product Strategy and Development, BNY	None
Trustee	Serves until a successor	Mellon Investment Management (investment management firm) (2012-2018);
	trustee is elected or	Vice Chairman – The Dreyfus Corporation (2005 – 2018): Executive Vice
	earlier retirement	President Head of Product, BNY Mellon Investment Management
	or removal.	(2007-2012); Executive Director- Product Strategy, Mellon Asset Management
		(2005-2007); Executive Vice President Head of Products, Marketing and
		Client Service, Dreyfus Corporation (investment management firm)
		(2000-2005); and Senior Vice President Strategic Product and Business
		Development, Dreyfus Corporation (1994-2000)

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Name, Age and Position	Term of Office and		Other Directorships
Held With the Fund	Length of Service	Principal Occupation	Held by Trustee
Benjamin M. Friedman (76)	Trustee since 2008.	William Joseph Maier Professor of Political Economy, Harvard University	Trustee, Mellon Institutional Funds
Trustee	Serves until a successor	(1972 – present)	Investment Trust and Mellon
	trustee is elected or		Institutional Funds Master Portfolio
	earlier retirement		(oversaw 17 portfolios in fund
	or removal.		complex) (1989 - 2008)
Lorraine H. Monchak (64)	Trustee since 2017.	Chief Investment Officer, 1199 SEIU Funds (healthcare workers union	None
Trustee	(Advisory Trustee from	pension funds) (2001 – present); Vice President – International Investments
	2014 - 2017). Serves	Group, American International Group, Inc. (insurance company)
	until a successor trustee	(1993 – 2001); Vice President – Corporate Finance and Treasury Group,
	is elected or earlier	Citibank, N.A. (1980 – 1986 and 1990 – 1993); Vice President – Asset/Liability
	retirement or removal.	Management Group, Federal Farm Funding Corporation
		(government-sponsored issuer of debt securities) (1988 – 1990); Mortgage
		Strategies Group, Shearson Lehman Hutton, Inc. (investment bank)
		(1987 – 1988); and Mortgage Strategies Group, Drexel Burnham Lambert,
		Ltd. (investment bank) (1986 – 1987)
Marguerite A. Piret (72)	Trustee since 1998.	Chief Financial Officer, American Ag Energy, Inc. (controlled environment	Director of New America High
Trustee	Serves until a successor	and agriculture company) (2016 – present); and President and Chief	Income Fund, Inc. (closed-end
	trustee is elected or	Executive Officer, Metric Financial Inc. (formerly known as Newbury Piret	investment company)
	earlier retirement	Company) (investment banking firm) (1981 – 2019)	(2004 – present); and Member,
	or removal.		Board of Governors, Investment
			Company Institute (2000 – 2006)

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Independent Trustees (continued)


Name, Age and Position	Term of Office and		Other Directorships
Held With the Fund	Length of Service	Principal Occupation	Held by Trustee
Fred J. Ricciardi (73)	Trustee since 2014.	Private investor (2020 – present); Consultant (investment company services)	None
Trustee	Serves until a successor	(2012 – 2020); Executive Vice President, BNY Mellon (financial and
	trustee is elected or	investment company services) (1969 – 2012); Director, BNY International
	earlier retirement	Financing Corp. (financial services) (2002 – 2012); Director, Mellon
	or removal.	Overseas Investment Corp. (financial services) (2009 – 2012); Director,
		Financial Models (technology) (2005-2007); Director, BNY Hamilton Funds,
		Ireland (offshore investment companies) (2004-2007); Chairman/Director,
		AIB/BNY Securities Services, Ltd., Ireland (financial services) (1999-2006);
		and Chairman, BNY Alternative Investment Services, Inc. (financial services)
		(2005-2007)

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Interested Trustees


Name, Age and Position	Term of Office and		Other Directorships
Held With the Fund	Length of Service	Principal Occupation	Held by Trustee
Lisa M. Jones (58)*	Trustee since 2017.	Director, CEO and President of Amundi Pioneer Asset Management USA,	None
Trustee, President and	Serves until a successor	Inc. (investment management firm) (since September 2014); Director, CEO
Chief Executive Officer	trustee is elected or	and President of Amundi Pioneer Asset Management, Inc. (since
	earlier retirement	September 2014); Director, CEO and President of Amundi Pioneer
	or removal	Distributor, Inc. (since September 2014); Director, CEO and President of
		Amundi Pioneer Institutional Asset Management, Inc. (since September 2014);
		Chair, Amundi Pioneer Asset Management USA, Inc., Amundi Pioneer
		Distributor, Inc. and Amundi Pioneer Institutional Asset Management, Inc.
		(September 2014 – 2018); Managing Director, Morgan Stanley Investment
		Management (investment management firm) (2010 – 2013); Director of
		Institutional Business, CEO of International, Eaton Vance Management
		(investment management firm) (2005 – 2010); and Director of
		Amundi USA, Inc. (since 2017)
Kenneth J. Taubes (62)*	Trustee since 2014.	Director and Executive Vice President (since 2008) and Chief Investment	None
Trustee	Serves until a successor	Officer, U.S. (since 2010) of Amundi Pioneer Asset Management USA, Inc.
	trustee is elected or	(investment management firm); Director and Executive Vice President and
	earlier retirement	Chief Investment Officer, U.S. of Amundi (since 2008); Executive
	or removal	Vice President and Chief Investment Officer, U.S. of Amundi Pioneer
		Institutional Asset Management, Inc. (since 2009); Portfolio Manager of
		Amundi (since 1999); and Director of Amundi USA, Inc. (since 2017)

* Ms. Jones and Mr. Taubes are Interested Trustees because they are officers or directors of the Fund’s investment adviser and certain of its affiliates.

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Fund Officers


Name, Age and Position	Term of Office and		Other Directorships
Held With the Fund	Length of Service	Principal Occupation	Held by Officer
Christopher J. Kelley (55)	Since 2010. Serves at	Vice President and Associate General Counsel of Amundi since	None
Secretary and Chief	the discretion of	January 2008; Secretary and Chief Legal Officer of all of the Pioneer Funds
Legal Officer	the Board	since June 2010; Assistant Secretary of all of the Pioneer Funds from
		September 2003 to May 2010; and Vice President and Senior Counsel of
		Amundi from July 2002 to December 2007
Carol B. Hannigan (59)	Since 2010. Serves at	Fund Governance Director of Amundi since December 2006 and	None
Assistant Secretary	the discretion of	Assistant Secretary of all the Pioneer Funds since June 2010;
	the Board	Manager – Fund Governance of Amundi from December 2003 to
		November 2006; and Senior Paralegal of Amundi from
		January 2000 to November 2003
Thomas Reyes (57)	Since 2010. Serves at	Assistant General Counsel of Amundi since May 2013 and	None
Assistant Secretary	the discretion of	Assistant Secretary of all the Pioneer Funds since June 2010; and Counsel of
	the Board	Amundi from June 2007 to May 2013
Mark E. Bradley (60)	Since 2008. Serves at	Vice President – Fund Treasury of Amundi; Treasurer of all of the	None
Treasurer and	the discretion of	Pioneer Funds since March 2008; Deputy Treasurer of Amundi
Chief Financial and	the Board	from March 2004 to February 2008; and Assistant Treasurer of all of the
Accounting Officer		Pioneer Funds from March 2004 to February 2008
Luis I. Presutti (55)	Since 1998. Serves at	Director – Fund Treasury of Amundi; and Assistant Treasurer of	None
Assistant Treasurer	the discretion of	all of the Pioneer Funds
	the Board
Gary Sullivan (62)	Since 2002. Serves at	Senior Manager – Fund Treasury of Amundi; and Assistant Treasurer	None
Assistant Treasurer	the discretion of	of all of the Pioneer Funds
	the Board

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Name, Age and Position	Term of Office and		Other Directorships
Held With the Fund	Length of Service	Principal Occupation	Held by Officer
Antonio Furtado (38)	Since 2020. Serves at	Fund Oversight Manager – Fund Treasury of Amundi; and Assistant	None
Assistant Treasurer	the discretion of	Treasurer of all of the Pioneer Funds
	the Board
John Malone (48)	Since 2018. Serves at	Managing Director, Chief Compliance Officer of Amundi Pioneer Asset	None
Chief Compliance Officer	the discretion of	Management; Amundi Pioneer Institutional Asset Management, Inc.; and
	the Board	the Pioneer Funds since September 2018; and Chief Compliance Officer of
		Amundi Pioneer Distributor, Inc. since January 2014.
Kelly O’Donnell (49)	Since 2006. Serves at	Vice President – Amundi Pioneer Asset Management; and Anti-Money	None
Anti-Money	the discretion of	Laundering Officer of all the Pioneer Funds since 2006
Laundering Officer	the Board

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How to Contact Amundi

We are pleased to offer a variety of convenient ways for you to contact us for assistance or information.


Call us for:
Account Information, including existing accounts,
new accounts, prospectuses, applications
and service forms		1-800-225-6292

FactFone^SMfor automated fund yields, prices,
account information and transactions		1-800-225-4321

Retirement plans information		1-800-622-0176

Write to us:
Amundi
P.O. Box 219427
Kansas City, MO 64121-9427

Our toll-free fax		1-800-225-4240

Our internet e-mail address	us.askamundipioneer@amundipioneer.com
(for general questions about Amundi only)

Visit our web site: www.amundipioneer.com/us

This report must be preceded or accompanied by a prospectus.

The Fund files a complete schedule of portfolio holdings with the Securities and Exchange Commission for the first and third quarters of each fiscal year as an exhibit to its reports on Form N-PORT. Shareholders may view the filed Form N-PORT by visiting the Commission’s web site at https://www.sec.gov.

Amundi Pioneer Asset Management, Inc.
60 State Street
Boston, MA 02109
www.amundipioneer.com/us

Securities offered through Amundi Pioneer Distributor, Inc.
60 State Street, Boston, MA 02109
Underwriter of Pioneer Mutual Funds, Member SIPC
© 2020 Amundi Pioneer Asset Management 19441-14-1220

ITEM 2. CODE OF ETHICS.

(a) Disclose whether, as of the end of the period covered by the report, the registrant has adopted a code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party. If the registrant has not adopted such a code of ethics, explain why it has not done so.

The registrant has adopted, as of the end of the period covered by this report, a code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer and controller.

(b) For purposes of this Item, the term “code of ethics” means written standards that are reasonably designed to deter wrongdoing and to promote:

(1) Honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships;

(2) Full, fair, accurate, timely, and understandable disclosure in reports and documents that a registrant files with, or submits to, the Commission and in other public communications made by the registrant;

(3) Compliance with applicable governmental laws, rules, and regulations;

(4) The prompt internal reporting of violations of the code to an appropriate person or persons identified in the code; and

(5) Accountability for adherence to the code.

(c) The registrant must briefly describe the nature of any amendment, during the period covered by the report, to a provision of its code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, and that relates to any element of the code of ethics definition enumerated in paragraph (b) of this Item. The registrant must file a copy of any such amendment as an exhibit pursuant to Item 10(a), unless the registrant has elected to satisfy paragraph (f) of this Item by posting its code of ethics on its website pursuant to paragraph (f)(2) of this Item, or by undertaking to provide its code of ethics to any person without charge, upon request, pursuant to paragraph (f)(3) of this Item.

The registrant has made no amendments to the code of ethics during the period covered by this report.

(d) If the registrant has, during the period covered by the report, granted a waiver, including an implicit waiver, from a provision of the code of ethics to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, that relates to one or more of the items set forth in paragraph (b) of this Item, the registrant must briefly describe the nature of the waiver, the name of the person to whom the waiver was granted, and the date of the waiver.

Not applicable.

(e) If the registrant intends to satisfy the disclosure requirement under paragraph (c) or (d) of this Item regarding an amendment to, or a waiver from, a provision of its code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions and that relates to any element of the code of ethics definition

enumerated in paragraph (b) of this Item by posting such information on its Internet website, disclose the registrant’s Internet address and such intention.

Not applicable.

(f) The registrant must:

(1) File with the Commission, pursuant to Item 12(a)(1), a copy of its code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, as an exhibit to its annual report on this Form N-CSR (see attachment);

(2) Post the text of such code of ethics on its Internet website and disclose, in its most recent report on this Form N-CSR, its Internet address and the fact that it has posted such code of ethics on its Internet website; or

(3) Undertake in its most recent report on this Form N-CSR to provide to any person without charge, upon request, a copy of such code of ethics and explain the manner in which such request may be made. See Item 10(2)

ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT.

(a) (1) Disclose that the registrant’s board of trustees has determined that the registrant either:

(i) Has at least one audit committee financial expert serving on its audit committee; or

(ii) Does not have an audit committee financial expert serving on its audit committee.

The registrant’s Board of Trustees has determined that the registrant has at least one audit committee financial expert.

(2) If the registrant provides the disclosure required by paragraph (a)(1)(i) of this Item, it must disclose the name of the audit committee financial expert and whether that person is “independent.” In order to be considered “independent” for purposes of this Item, a member of an audit committee may not, other than in his or her capacity as a member of the audit committee, the board of trustees, or any other board committee:

(i) Accept directly or indirectly any consulting, advisory, or other compensatory fee from the issuer; or

(ii) Be an “interested person” of the investment company as defined in Section 2(a)(19) of the Act (15 U.S.C. 80a-2(a)(19)).

Mr. Fred J. Ricciardi, an independent trustee, is such an audit committee financial expert.

(3) If the registrant provides the disclosure required by paragraph (a)(1) (ii) of this Item, it must explain why it does not have an audit committee financial expert.

Not applicable.

ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES.

(a) Disclose, under the caption AUDIT FEES, the aggregate fees billed for each of the last two fiscal years for professional services rendered by the principal accountant for the audit of the registrant’s annual financial statements or services that are normally provided by the accountant in connection with statutory and regulatory filings or engagements for those fiscal years.

The audit fees for the Fund were $48,900 payable to Ernst & Young LLP for the year ended October 31, 2020 and $45,000 for the year ended October 31, 2019.

(b) Disclose, under the caption AUDIT-RELATED FEES, the aggregate fees billed in each of the last two fiscal years for assurance and related services by the principal accountant that are reasonably related to the performance of the audit of the registrant’s financial statements and are not reported under paragraph (a) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category.

There were no audit-related services in 2020 or 2019.

(c) Disclose, under the caption TAX FEES, the aggregate fees billed in each of the last two fiscal years for professional services rendered by the principal accountant for tax compliance, tax advice, and tax planning. Registrants shall describe the nature of the services comprising the fees disclosed under this category.

The Fund paid aggregate non-audit fees to Ernst & Young LLP for tax services of $18,754 and $10,115 during the fiscal years ended October 31, 2020 and 2019, respectively.

(d) Disclose, under the caption ALL OTHER FEES, the aggregate fees billed in each of the last two fiscal years for products and services provided by the principal accountant, other than the services reported in paragraphs (a) through (c) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category.

There were no other fees in 2020 or 2019.

(e) (1) Disclose the audit committee’s pre-approval policies and procedures described in paragraph (c)(7) of Rule 2-01 of Regulation S-X.

PIONEER FUNDS

APPROVAL OF AUDIT, AUDIT-RELATED, TAX AND OTHER SERVICES

PROVIDED BY THE INDEPENDENT AUDITOR

SECTION I - POLICY PURPOSE AND APPLICABILITY

The Pioneer Funds recognize the importance of maintaining the independence of their outside auditors. Maintaining independence is a shared responsibility involving Amundi Pioneer Asset Management, Inc, the audit committee and the independent auditors.

The Funds recognize that a Fund’s independent auditors: 1) possess knowledge of the Funds, 2) are able to incorporate certain services into the scope of the audit, thereby avoiding redundant work, cost and disruption of Fund personnel and processes, and 3) have expertise that has value to the Funds. As a result, there are situations where it is desirable to use the Fund’s independent auditors for services in addition to the annual audit and where the potential for conflicts of interests are minimal. Consequently, this policy, which is intended to comply with Rule 210.2-01(C)(7), sets forth guidelines and procedures to

be followed by the Funds when retaining the independent audit firm to perform audit, audit-related tax and other services under those circumstances, while also maintaining independence.

Approval of a service in accordance with this policy for a Fund shall also constitute approval for any other Fund whose pre-approval is required pursuant to Rule 210.2-01(c)(7)(ii).

In addition to the procedures set forth in this policy, any non-audit services that may be provided consistently with Rule 210.2-01 may be approved by the Audit Committee itself and any pre-approval that may be waived in accordance with Rule 210.2-01(c)(7)(i)(C) is hereby waived.

Selection of a Fund’s independent auditors and their compensation shall be determined by the Audit Committee and shall not be subject to this policy.


SECTION II - POLICY

SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION	SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES

I. AUDIT SERVICES	Services that are directly	o Accounting research assistance
	related to performing the	o SEC consultation, registration
	independent audit of the Funds	statements, and reporting
		o Tax accrual related matters
		o Implementation of new accounting standards
		o Compliance letters (e.g. rating agency letters)
		o Regulatory reviews and assistance
		regarding financial matters
		o Semi-annual reviews (if requested)
		o Comfort letters for closed end offerings
II. AUDIT-RELATED	Services which are not	o AICPA attest and agreed-upon procedures
SERVICES	prohibited under Rule	o Technology control assessments
	210.2-01(C)(4) (the “Rule”)	o Financial reporting control assessments
	and are related extensions of	o Enterprise security architecture
	the audit services support the	assessment
	audit, or use the knowledge/expertise
	gained from the audit procedures as a
	foundation to complete the project.
	In most cases, if the Audit-Related
	Services are not performed by the
	Audit firm, the scope of the Audit
	Services would likely increase.
	The Services are typically well-defined
	and governed by accounting
	professional standards (AICPA,
	SEC, etc.)

AUDIT COMMITTEE APPROVAL POLICY		AUDIT COMMITTEE REPORTING POLICY
o “One-time” pre-approval		o A summary of all such
for the audit period for all		services and related fees
pre-approved specific service		reported at each regularly
subcategories. Approval of the		scheduled Audit Committee
independent auditors as		meeting.
auditors for a Fund shall
constitute pre approval for
these services.

o “One-time” pre-approval		o A summary of all such
for the fund fiscal year within		services and related fees
a specified dollar limit		(including comparison to
for all pre-approved		specified dollar limits)
specific service subcategories		reported quarterly.

o Specific approval is
needed to exceed the
pre-approved dollar limit for
these services (see general
Audit Committee approval policy
below for details on obtaining
specific approvals)

o Specific approval is
needed to use the Fund’s
auditors for Audit-Related
Services not denoted as
“pre-approved”, or
to add a specific service
subcategory as “pre-approved”

SECTION III - POLICY DETAIL, CONTINUED


SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION	SPECIFIC PRE-APPROVED SERVICE
		SUBCATEGORIES
III. TAX SERVICES	Services which are not	o Tax planning and support
	prohibited by the Rule,	o Tax controversy assistance
	if an officer of the Fund	o Tax compliance, tax returns, excise
	determines that using the	tax returns and support
	Fund’s auditor to provide	o Tax opinions
	these services creates
	significant synergy in
	the form of efficiency,
	minimized disruption, or
	the ability to maintain a
	desired level of
	confidentiality.


AUDIT COMMITTEE APPROVAL POLICY	AUDIT COMMITTEE REPORTING POLICY
o “One-time” pre-approval	o A summary of
for the fund fiscal year	all such services and
within a specified dollar limit	related fees
	(including comparison
	to specified dollar
	limits) reported
	quarterly.

o Specific approval is
needed to exceed the
pre-approved dollar limits for
these services (see general
Audit Committee approval policy
below for details on obtaining
specific approvals)

o Specific approval is
needed to use the Fund’s
auditors for tax services not
denoted as pre-approved, or to
add a specific service subcategory as
“pre-approved”

SECTION III - POLICY DETAIL, CONTINUED


SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION	SPECIFIC PRE-APPROVED SERVICE
		SUBCATEGORIES
IV. OTHER SERVICES	Services which are not	o Business Risk Management support
	prohibited by the Rule,	o Other control and regulatory
A. SYNERGISTIC,	if an officer of the Fund	compliance projects
UNIQUE QUALIFICATIONS	determines that using the
	Fund’s auditor to provide
	these services creates
	significant synergy in
	the form of efficiency,
	minimized disruption,
	the ability to maintain a
	desired level of
	confidentiality, or where
	the Fund’s auditors
	posses unique or superior
	qualifications to provide
	these services, resulting
	in superior value and
	results for the Fund.


AUDIT COMMITTEE APPROVAL POLICY	AUDIT COMMITTEE REPORTING POLICY
o “One-time” pre-approval	o A summary of
for the fund fiscal year within	all such services and
a specified dollar limit	related fees
	(including comparison
	to specified dollar
	limits) reported
	quarterly.
o Specific approval is
needed to exceed the
pre-approved dollar limits for
these services (see general
Audit Committee approval policy
below for details on obtaining
specific approvals)

o Specific approval is
needed to use the Fund’s
auditors for “Synergistic” or
“Unique Qualifications” Other
Services not denoted as
pre-approved to the left, or to
add a specific service
subcategory as “pre-approved”

SECTION III - POLICY DETAIL, CONTINUED


SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION	SPECIFIC PROHIBITED SERVICE
		SUBCATEGORIES
PROHIBITED SERVICES	Services which result	1. Bookkeeping or other services
	in the auditors losing	related to the accounting records or
	independence status	financial statements of the audit
	under the Rule.	client*
		2. Financial information systems design
		and implementation*
		3. Appraisal or valuation services,
		fairness* opinions, or
		contribution-in-kind reports
		4. Actuarial services (i.e., setting
		actuarial reserves versus actuarial
		audit work)*
		5. Internal audit outsourcing services*
		6. Management functions or human
		resources
		7. Broker or dealer, investment
		advisor, or investment banking services
		8. Legal services and expert services
		unrelated to the audit
		9. Any other service that the Public
		Company Accounting Oversight Board
		determines, by regulation, is
		impermissible


AUDIT COMMITTEE APPROVAL POLICY	AUDIT COMMITTEE REPORTING POLICY
o These services are not to be	o A summary of all
performed with the exception of the(*)	services and related
services that may be permitted	fees reported at each
if they would not be subject to audit	regularly scheduled
procedures at the audit client (as	Audit Committee meeting
defined in rule 2-01(f)(4)) level	will serve as continual
the firm providing the service.	confirmation that has
	not provided any
	restricted services.

GENERAL AUDIT COMMITTEE APPROVAL POLICY:

o For all projects, the officers of the Funds and the Fund’s auditors will each make an assessment to determine that any proposed projects will not impair independence.

o Potential services will be classified into the four non-restricted service categories and the “Approval of Audit, Audit-Related, Tax and Other Services�� Policy above will be applied. Any services outside the specific pre-approved service subcategories set forth above must be specifically approved by the Audit Committee.

o At least quarterly, the Audit Committee shall review a report summarizing the services by service category, including fees, provided by the Audit firm as set forth in the above policy.

(2) Disclose the percentage of services described in each of paragraphs (b) through (d) of this Item that were approved by the audit committee pursuant to paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X.

Non-Audit Services

Beginning with non-audit service contracts entered into on or after May 6, 2003, the effective date of the new SEC pre-approval rules, the Fund's audit committee is required to pre-approve services to affiliates defined by SEC rules to the extent that the services are determined to have a direct impact on the operations or financial reporting of the Fund. For the years ended October 31, 2020 and 2019, there were no services provided to an affiliate that required the Fund's audit committee pre-approval.

(f) If greater than 50 percent, disclose the percentage of hours expended on the principal accountants engagement to audit the registrant’s financial statements for the most recent fiscal year that were attributed to work performed by persons other than the principal accountant’s full-time, permanent employees.

N/A

(g) Disclose the aggregate non-audit fees billed by the registrants accountant for services rendered to the registrant, and rendered to the registrants investment adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant for each of the last two fiscal years of the registrant.

The Fund paid aggregate non-audit fees to Ernst & Young LLP for tax services of $18,754 and $10,115 during the fiscal years ended October 31, 2020 and 2019, respectively.

(h) Disclose whether the registrants audit committee of the board of trustees has considered whether the provision of non-audit services that were rendered to the registrants investment adviser (not including any subadviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant’s independence.

The Fund’s audit committee of the Board of Trustees has considered whether the provision of non-audit services that were rendered to the Affiliates (as defined) that were not pre- approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant’s independence.

ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS

(a) If the registrant is a listed issuer as defined in Rule 10A-3 under the Exchange Act (17 CFR 240.10A-3), state whether or not the registrant has a separately-designated standing audit committee established in accordance with Section 3(a)(58)(A) of the Exchange Act (15 U.S.C. 78c(a)(58)(A)). If the registrant has such a committee, however designated, identify each committee member. If the entire board of directors is acting as the registrant’s audit committee as specified in Section 3(a)(58)(B) of the Exchange Act (15 U.S.C. 78c(a)(58)(B)), so state.

N/A

(b) If applicable, provide the disclosure required by Rule 10A-3(d) under the Exchange Act (17 CFR 240.10A-3(d)) regarding an exemption from the listing standards for audit committees.

N/A

ITEM 6. SCHEDULE OF INVESTMENTS.

File Schedule of Investments in securities of unaffiliated issuers as of the close of the reporting period as set forth in 210.1212 of Regulation S-X [17 CFR 210.12-12], unless the schedule is included as part of the report to shareholders filed under Item 1 of this Form.

Included in Item 1

ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

A closed-end management investment company that is filing an annual report on this Form N-CSR must, unless it invests exclusively in non-voting securities, describe the policies and procedures that it uses to determine how to vote proxies relating to portfolio securities, including the procedures that the company uses when a vote presents a conflict between the interests of its shareholders, on the one hand, and those of the company’s investment adviser; principal underwriter; or any affiliated person (as defined in Section 2(a)(3) of the Investment Company Act of 1940 (15 U.S.C. 80a-2(a)(3)) and the rules thereunder) of the company, its investment adviser, or its principal underwriter, on the other. Include any policies and procedures of the company’s investment adviser, or any other third party, that the company uses, or that are used on the company’s behalf, to determine how to vote proxies relating to portfolio securities.

N/A

ITEM 8. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

(a) If the registrant is a closed-end management investment company that is filing an annual report on this Form N-CSR, provide the following information:

(1) State the name, title, and length of service of the person or persons employed by or associated with the registrant or an investment adviser of the registrant who are primarily responsible for the day-to-day management of the registrant’s portfolio (“Portfolio Manager”). Also state each Portfolio Manager’s business experience during the past 5 years.

N/A

ITEM 9. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS.

(a) If the registrant is a closed-end management investment company, in the following tabular format, provide the information specified in paragraph (b) of this Item with respect to any purchase made by or on behalf of the registrant or any affiliated purchaser, as defined in Rule 10b-18(a)(3) under the Exchange Act (17 CFR 240.10b-18(a)(3)), of shares or other units of any class of the registrant’s equity securities that is registered by the registrant pursuant to Section 12 of the Exchange Act (15 U.S.C. 781).

N/A

ITEM 10. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

Describe any material changes to the procedures by which shareholders may recommend nominees to the registrant’s board of directors, where those changes were implemented after the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R(17 CFR 229.407)(as required by Item 22(b)(15)) of Schedule 14A (17 CFR 240.14a-101), or this Item.

There have been no material changes to the procedures by which the shareholders may recommend nominees to the registrant’s board of directors since the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R of Schedule 14(A) in its definitive proxy statement, or this item.

ITEM 11. CONTROLS AND PROCEDURES.

(a) Disclose the conclusions of the registrant’s principal executive and principal financials officers, or persons performing similar functions, regarding the effectiveness of the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Act (17 CFR 270.30a-3(c))) as of a date within 90 days of the filing date of the report that includes the disclosure required by this paragraph, based on the evaluation of these controls and procedures required by Rule 30a-3(b) under the Act (17 CFR 270.30(a)-3(b) and Rules 13a-15(b) or 15d-15(b) under the Exchange Act (17 CFR 240.13a-15(b) or 240.15d-15(b)).

The registrant’s principal executive officer and principal financial officer have concluded that the registrant’s disclosure controls and procedures are effective based on the evaluation of these controls and procedures as of a date within 90 days of the filing date of this report.

(b) Disclose any change in the registrant’s internal control over financial reporting (as defined in Rule 30a-3(d) under the Act (17CFR 270.30a-3(d)) that occured during the second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting.

There were no significant changes in the registrant’s internal control over financial reporting that occurred during the second fiscal quarter of the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12. Disclosure of Securities Lending Activities for Closed-End Management Investment Companies.

(a) If the registrant is a closed-end management investment company, provide the following dollar amounts of income and compensation related to the securities lending activities of the registrant during its most recent fiscal year:

N/A

(1) Gross income from securities lending activities;

N/A

(2) All fees and/or compensation for each of the following securities lending activities and related services: any share of revenue generated by the securities lending program paid to the securities lending agent(s) (revenue split); fees paid for cash collateral management services (including fees deducted from a pooled cash collateral reinvestment vehicle) that are not included in the revenue split; administrative fees that are not included in the revenue split; fees for indemnification that are not included in the revenue split; rebates paid to borrowers; and any other fees relating to the securities lending program that are not included in the revenue split, including a description of those other fees;

N/A

(3) The aggregate fees/compensation disclosed pursuant to paragraph (2); and

N/A

(4) Net income from securities lending activities (i.e., the dollar amount in paragraph (1) minus the dollar amount in paragraph (3)).

If a fee for a service is included in the revenue split, state that the fee is included in the revenue split.

N/A

(b) If the registrant is a closed-end management investment company, describe the services provided to the registrant by the securities lending agent in the registrants most recent fiscal year.

N/A

ITEM 13. EXHIBITS.

(a) File the exhibits listed below as part of this Form. Letter or number the exhibits in the sequence indicated.

(1) Any code of ethics, or amendment thereto, that is the subject of the disclosure required by Item 2, to the extent that the registrant intends to satisfy the Item 2 requirements through filing of an exhibit.

(2) A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the Act (17 CFR 270.30a-2(a)) , exactly as set forth below:

Filed herewith.

SIGNATURES

[See General Instruction F]

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant) Pioneer High Yield Fund

By (Signature and Title)* /s/ Lisa M. Jones

Lisa M. Jones, President & Chief Executive Officer

Date December 30, 2020

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)* /s/ Lisa M. Jones

Lisa M. Jones, President & Chief Executive Officer

Date December 30, 2020

By (Signature and Title)* /s/ Mark E. Bradley

Mark E. Bradley, Treasurer & Chief Accounting & Financial Officer

Date December 30, 2020

* Print the name and title of each signing officer under his or her signature.

Pioneer High Yield Fund N-CSRCertified annual shareholder report (management investment company)