Pioneer Series Trust Ii N-CSRSCertified semi-annual shareholder report (management investment company)

capacity to try and catch up with a broad-based shortage in semiconductors as well as booming demand for advanced chips driven by 5G networks, remote working, electric cars, and artificial intelligence applications. Those applications have been among the leading drivers of Lam’s etching and deposition-device sales.

Generac is a leading manufacturer of a broad range of residential standby and portable generators, with a dominant market share in the North American standby generator market as well as a leading position in portable generators. Generac’s shares outperformed during the six-month period as the company benefited from increased demand for its products, driven by factors such as wildfires in California, an active hurricane season in the Atlantic, and the COVID-19 pandemic, which kept people across the country inside their homes for months. All of those issues helped generate greater interest in Generac’s backup-power solutions. Additionally, the company delivered yet another strong financial report for its fiscal fourth quarter of 2020, which handily beat “Street” estimates. We believe Generac could continue to benefit from its strong product positioning as well as a rapidly expanding clean-energy market.

Micron Technology is one of the leading global providers of memory semiconductors used for applications such as data storage. The company’s share price rose during the six-month period as Micron reported strong financial results for both its fiscal first and second quarters. Investors have also become more confident that the memory industry could continue to experience supply constraints, which may in turn lead to strong demand, driven by growth in both 5G and data centers.

IAC/InterActive is a leading media and Internet company. The company operates some of the most globally recognized digital brands, ranging from digital media to e-commerce. IAC operates through multiple business segments, including: ANGI Homeservices, Dotdash, and Emerging & Other. IAC’s share price rose during the six-month period. The company successfully spun-off its majority ownership of Vimeo, and investors were able to better appreciate the value of IAC’s remaining assets. (The Fund held a position in Vimeo as of May 31, 2021.) Another positive factor for IAC during the period was the release of financial results showing a smaller decline in online advertising demand for its media properties (due to the COVID-19-induced economic shutdowns) than had been previously feared.

Individual stocks that detracted from the Fund’s benchmark-relative performance during the six-month period included positions in Mirati Therapeutics and Fibrogen, and lack of portfolio exposure to Fortinet and Simon Property Group.

Mirati Therapeutics is a clinical-stage oncology company developing therapies for genetically defined tumors. The company has two leading drug candidates for hard-to-treat cancer indications that have been advancing rapidly in clinical trials. Mirati’s share price declined over the six-month period, falling victim to a broad market sell-off in biotech stocks of companies viewed as having earnings potential in future years. We have maintained a portfolio overweight position in Mirati versus the benchmark, as we believe the company could be successful in commercializing its development-stage drugs, which we think feature well-differentiated product profiles.

Fibrogen has focused on the development of two potential first-in-class drug candidates, including Rokadustat, a treatment for anemia associated with chronic kidney disease. Fibrogen’s shares underperformed during the period after the company made a clarification to the cardiovascular safety analysis of its Roxadustat drug, which investors perceived as a potential negative for the drug’s future sales potential. We sold the Fund’s position in Fibrogen during the period.

Not owning shares of Russell Index member Fortinet, a provider of network-security solutions, hurt the Fund’s benchmark-relative returns for the six-month period. The company’s share price rose as Fortinet benefited from an environment of increased demand for network-security solutions. While the Fund did not have a position in Fortinet, the portfolio did own shares of other security-related companies that experienced solid performance over the period, but those positives were not sufficient to offset the negative effects of the lack of exposure to Fortinet.

Simon Property Group is another Russell Index member that performed well during the period, and the Fund’s lack of exposure to the stock detracted from relative returns. Simon is a real estate investment trust (REIT) which owns, develops, and manages retail real estate properties, including regional malls. Simon’s share price increased over the period as investors appeared to conclude that the expanding distribution of COVID-19 vaccines combined with pent-up consumer demand for physical (in-person) retail spending could likely benefit Simon’s business in the second half of the calendar year.

On the positive side, the pace of the rollout of COVID-19 vaccinations has been surpassing previous estimates, which could lead to a complete “return to normal” for the economy in the second half of the calendar year. That, in turn, could unleash significant pent-up demand and robust economic growth in the US. In addition, the accommodative monetary policies of the Federal Reserve (Fed) seem likely to continue into 2022, based on the Fed’s recent pronouncements; meanwhile, the latest round of US government fiscal stimulus, totaling $1.9 trillion, has “added fuel to the fire.” Moreover, a proposed federal infrastructure spending initiative currently under consideration and debate could provide still more stimulus.

On the negative side, the forecasted significant increase in economic demand may overwhelm supply to the point that inflation ramps up at a faster-than-expected pace. A faster rise in the rate of inflation could result in a further, rapid increase in long-term interest rates, which might be a potential negative for equity prices. Additionally, if investors believe that the Fed may likely fall behind the curve in letting inflation rise too quickly, equities could sell off on inflation fears, which might trigger an even broader market sell-off. Another issue that bears watching is the US government’s already high debt level, which has been ballooning due to the stimulus spending needed to help offset the effects of the pandemic on the economy. There could be a price to pay in the future, with equity markets likely beginning to discount that negative factor sometime down the road.

On the government-policy side, the power shift in both the Executive Branch and in Congress last January could lead to tax increases on both businesses and individuals, including a rise in the capital gains tax. In fact, earlier this year, the Biden administration floated the idea of a large tax hike. An increase to the capital gains tax rate could discourage investments in equities as individuals attempt to avoid realizing capital gains. Businesses, too, could curtail both hiring and spending to offset the effects of higher taxes on their bottom lines. Such a scenario could lead to an eventual, substantial weakening in both corporate earnings and economic activity.

In the end, however, we believe investors are likely to favor owning stocks of well-positioned secular growth companies with reasonable valuations that are not highly dependent on positive macroeconomic

conditions in order to flourish. Companies that they believe have resilient business models, and companies that can exhibit sustainable growth characteristics and innovation. Those characteristics typify the types of equities that we seek to hold in the Fund’s portfolio.

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.

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.

Securities 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 May 31, 2021, no securities were valued using fair value methods (other than securities valued using prices supplied by independent pricing services, broker-dealers or using a third party insurance industry pricing model).

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.

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.

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.

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.

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 November 30, 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.

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.

The tax character of current year distributions payable will be determined at the end of the current taxable year. The tax character of distributions paid during the year ended November 30, 2020 was as follows:

The Fund records sales and repurchases of its shares as of trade date. The Distributor earned $25,256 in underwriting commissions on the sale of Class A shares during the six months ended May 31, 2021.

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 5). Class K and 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 4).

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 K, Class R and Class Y shares can reflect different transfer agent and distribution expense rates.

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.

The Fund may invest in REIT securities, the value of which can fall for a variety of reasons, such as declines in rental income, fluctuating interest rates, poor property management, environmental liabilities, uninsured damage, increased competition, or changes in real estate tax laws.

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 the Adviser 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 the Adviser 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.

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.