Putnam
High Income
Securities Fund

Semiannual report
2 | 28 | 18

Consider these risks before investing: Lower-rated bonds may offer higher yields in return for more risk. Bond investments are subject to interest-rate risk (the risk of bond prices falling if interest rates rise) and credit risk (the risk of an issuer defaulting on interest or principal payments). Interest-rate risk is greater for longer-term bonds, and credit risk is greater for below-investment-grade bonds. Unlike bonds, funds that invest in bonds have fees and expenses. Bond prices may fall or fail to rise over time for several reasons, including general financial market conditions, changing market perceptions (including perceptions about the risk of default and expectations about changes in monetary policy or interest rates), changes in government intervention, and factors related to a specific issuer or industry. These and other factors may lead to increased volatility and reduced liquidity in the fund’s portfolio holdings. You can lose money by investing in the fund. The fund’s shares trade on a stock exchange at market prices, which may be lower than the fund’s net asset value.

Message from the Trustees

April 12, 2018

Dear Fellow Shareholder:

After an extended period of record advances and low volatility, the U.S. stock market encountered some challenges in early 2018. Following several turbulent days, the S&P 500 Index entered correction territory on February 8, 2018, closing more than 10% below its January 2018 peak. Global stock and bond markets have also struggled as concerns grow about rising inflation and interest rates.

While declines like this can be unsettling, seasoned investors recognize that they are natural and ultimately can restore balance in the financial markets. In this changing environment, Putnam’s experienced investment professionals continue to monitor risks and seek opportunities. They take a research-intensive approach to investing that includes risk management strategies designed to serve investors in all types of markets.

As always, we believe investors should maintain a well-diversified portfolio, think about long-term goals, and speak regularly with their financial advisors. In the following pages, you will find an overview of your fund’s performance for the reporting period as well as an outlook for the coming months.

Thank you for investing with Putnam.

Putnam High Income Securities Fund offers investors a portfolio of high-yield corporate bonds and convertible securities. As a closed-end fund, it shares some common characteristics with open-end mutual funds, but there are some key differences that investors should understand as they consider their portfolio.

Looking at a closed-end fund’s performance

You will usually see that the NAV and the market price differ. The market price can be influenced by several factors that cause it to vary from the NAV, including fund distributions, changes in supply and demand for the fund’s shares, changing market conditions, and investor perceptions of the fund or its investment manager. A fund’s performance at market price typically differs from its results at NAV.

A hybrid portfolio for seeking returns

Though it carries commensurately greater risk, including the risk of corporate default and periodic illiquidity, the fund’s combination of security types can offer greater return potential than other types of bond funds. This is because of the higher-yielding nature of below-investment-grade corporate credit and because of the optionality embedded in convertibles, which allows shares to be exchanged for common stock.

Data are historical. Past performance does not guarantee future results. More recent returns may be less or more than those shown. Investment return and net asset value will fluctuate, and you may have a gain or a loss when you sell your shares. Performance assumes reinvestment of distributions and does not account for taxes. Fund returns in the bar chart are at NAV. See below and pages 10–11 for additional performance information, including fund returns at market price. Index and Lipper results should be compared with fund performance at NAV.

* The fund’s blended benchmark is an unmanaged index administered by Putnam Management, 50% of which is the JPMorgan Developed High Yield Index and 50% of which is the ICE BofAML Speculative Grade U.S. Convertible Index. The ICE BofAML Speculative Grade U.S. Convertible Index and the JPMorgan Developed High Yield Index were introduced on 12/31/92 and 12/31/94, respectively, which post-date the inception of the fund.

† Returns for the six-month period are not annualized, but cumulative.

* The fund’s blended benchmark is an unmanaged index administered by Putnam Management, 50% of which is the JPMorgan Developed High Yield Index and 50% of which is the ICE BofAML Speculative Grade U.S. Convertible Index.

This comparison shows your fund’s performance in the context of broad market indexes for the six months ended 2/28/18. See above and pages 10–11 for additional fund performance information. Index descriptions can be found on page 12.

Robert L. Salvin
Portfolio Manager

Rob has an M.B.A. from the University of Chicago Booth School of Business and a B.S. from the University of Pennsylvania Wharton School. He joined Putnam in 2000 and has been in the investment industry since 1986.

Your fund is also managed by Anthony J. Daigle.

What contributed to the fund’s performance during the six-month reporting period ended February 28, 2018?

Conditions during the reporting period were generally favorable despite an increase in volatility in late January and February and concerns about valuations in corporate credit.

The convertibles portion of the portfolio, which represents a majority of assets, had positive absolute performance. Security selection within the consumer cyclicals and communication services sectors were the largest contributors on a relative basis. Specifically, an out-of-benchmark position in the consumer cyclical mobile payment company, Square, was one of the top relative performers at the issuer level. The underlying stock surged over the period in conjunction with the rest of the technology sector. An underweight position in DISH Network and an overweight position in Becton Dickinson also added to performance.

The high-yield portion of the portfolio also had positive absolute performance for the period. Overweight allocations to the financials; gaming, lodging and leisure; and utilities industries were the largest relative contributors to return. At the issuer level, positioning in Keane

Credit qualities are shown as a percentage of the fund’s net assets as of 2/28/18. A bond rated BBB or higher (A-3 or higher, for short-term debt) is considered investment grade. This chart reflects the highest security rating provided by one or more of Standard & Poor’s, Moody’s, and Fitch. Ratings and portfolio credit quality will vary over time.

Cash and net other assets, if any, represent the market value weights of cash, derivatives, and short-term securities in the portfolio. The fund itself has not been rated by an independent rating agency.

*Equity instruments are a combination of common stocks and convertible preferred stocks.

Group was the largest relative contributor. The portfolio had reduced exposure to the holding, which benefited performance due to Keane Group’s mixed to weaker third-quarter earnings results. In December, the fund’s position in Keane rallied. The holding was sold from the portfolio before period-end in January to lock in profits. Additionally, an underweight position in Ally Financial benefited returns, as the company posted constructive fourth-quarter earnings.

What detracted most from the fund’s benchmark-relative performance?

Underweight exposure to technology convertibles, along with security selection and a slight overweight position in the capital goods sector, were among the top detractors from relative performance. At the issuer level, underweight positioning in semiconductor companies Micron Technology and ON Semiconductor were the largest relative detractors. The underlying stocks all climbed in value during the period.

Among the portfolio’s high-yield holdings, underweight positions in the energy, health-care, and services industries were the largest relative detractors. At the issuer level, a moderate overweight allocation to CHS/Community Health Systems was the top detractor following weaker-than-expected fourth-quarter earnings. An overweight position in Sprint Communications also detracted from high-yield returns, as merger talks with T-Mobile USA collapsed during the fourth quarter.

Were there any noteworthy shifts in the fund’s asset allocation during the reporting period? If so, why?

In response to a rise in new issuance of convertible bonds, we have selectively participated in a few deals, resulting in a moderately higher allocation to convertible securities. The surge in new issuance that we have seen in the past few months has focused on convertible cash bonds, unlike the wave of mandatory convertibles that dominated the new-issue market prior

to the last year [mandatories automatically convert to stocks, causing them to trade essentially like stocks]. We believe there is relative value in the new-issue market, and so we have trimmed mandatories and replaced them when appropriate.

Additionally, higher Treasury yields and market expectations for three to four Federal Reserve rate hikes in 2018 led us to decrease exposure to convertible preferred stocks, which are more sensitive to interest-rate moves. As a result, the portfolio moved to a higher weighting in convertible bonds and notes.

What is your outlook for the coming months, and how has it influenced the fund’s positioning?

Investor confidence in the economy, coupled with solid underlying fundamentals, lead us to believe that the outlook for convertible securities remains constructive, although the sector has experienced some short-term volatility driven by inflation fears. The U.S. tax overhaul framework includes a reduction of the corporate tax rate, a lower repatriation tax rate, full expensing of capital expenditures, and the capping of interest deductibility. On balance, we believe these changes will be positive for convertible issuers. Additionally, the new tax law increases the relative attractiveness of convertible market funding versus corporate debt, particularly for more highly leveraged companies.

This table shows the fund’s top 10 individual holdings and the percentage of the fund’s net assets that each represented as of 2/28/18. Short-term investments and derivatives, if any, are excluded. Holdings may vary over time.

Convertibles witnessed a healthy new-issue market in 2017 and started 2018 with one of the strongest months in ten years as 14 deals were priced that together were worth $6.4 billion in proceeds in January. Increased supply has expanded the universe of investment options in the U.S. convertibles market, creating attractive associated return opportunities, in our view. We expect this robust environment for new issues to continue in the face of rising interest rates, barring any short-term volatility. Ultimately, with central banks beginning the process of normalizing monetary policy and potential equity market unease, we believe convertible securities continue to be an attractive option for investors whose investment objectives may include current income and capital appreciation while also lowering portfolio volatility.

In this environment, we favor what we view to be higher-quality names, along with higher market capitalization issuers. Additionally, we have trimmed exposure to securities in which the underlying equity valuations have become stretched, in our view.

We also continue to have a generally constructive view of the high-yield asset class as the fundamental landscape of U.S. issuers has been positive, buoyed by generally favorable corporate earnings and economic data. Additionally, we believe that many high-yield issuers should benefit from the lower corporate tax rate. Overall default levels have significantly fallen over the past 12 months and are at levels last seen in 2014. From a valuation standpoint, although spreads are measurably tighter year-over-year, they continue to look fair, in our view, on the back of solid fundamentals and are still wide of their all-time tights. The risks that we see include commodity price volatility, policy mistakes from global central banks, and/or heightened geopolitical tension. Overall, our positioning has been consistent, and we will continue to try to capitalize on what we believe

This chart shows how the fund’s weightings have changed over the past six months. Allocations are shown as a percentage of the fund’s net assets. Cash and net other assets, if any, represent the market value weights of cash, derivatives, short-term securities, and other unclassified assets in the portfolio. Current period summary information may differ from the portfolio schedule included in the financial statements due to the inclusion of derivative securities, the exclusion of as-of trades, if any, the use of different classifications of securities for presentation purposes, and rounding. Holdings and allocations may vary over time.

are relative value opportunities in the primary and secondary markets.

Thank you, Rob, for this update on the fund.

The views expressed in this report are exclusively those of Putnam Management and are subject to change. They are not meant as investment advice.

Please note that the holdings discussed in this report may not have been held by the fund for the entire period. Portfolio composition is subject to review in accordance with the fund’s investment strategy and may vary in the future. Current and future portfolio holdings are subject to risk.

Your fund’s performance

This section shows your fund’s performance, price, and distribution information for periods ended February 28, 2018, the end of the first half of its current fiscal year. In accordance with regulatory requirements for mutual funds, we also include performance information as of the most recent calendar quarter-end. Performance should always be considered in light of a fund’s investment strategy. Data represent past performance. Past performance does not guarantee future results. More recent returns may be less or more than those shown. Investment return, net asset value, and market price will fluctuate, and you may have a gain or a loss when you sell your shares.

Fund performance Total return for periods ended 2/28/18

Performance assumes reinvestment of distributions and does not account for taxes. Performance is shown net of expenses.

Comparative index returns For periods ended 2/28/18

Index and Lipper results should be compared with fund performance at net asset value.

^* Over the 6-month, 1-year, 3-year, 5-year, 10-year, and life-of-fund periods ended 2/28/18, there were 14, 13, 11, 11, 11, and 2 funds, respectively, in this Lipper category.

^† The fund’s blended benchmark is an unmanaged index administered by Putnam Management, 50% of which is the JPMorgan Developed High Yield Index and 50% of which is the ICE BofAML Speculative Grade U.S. Convertible Index. The ICE BofAML Speculative Grade U.S. Convertible Index and the JPMorgan Developed High Yield Index were introduced on 12/31/92 and 12/31/94, respectively, which post-date the inception of the fund.

Fund price and distribution information For the six-month period ended 2/28/18

The classification of distributions, if any, is an estimate. Final distribution information will appear on your year-end tax forms.

^* Most recent distribution, including any return of capital and excluding capital gains, annualized and divided by NAV or market price at end of period.

Fund performance as of most recent calendar quarter Total return for periods ended 3/31/18

See the discussion following the fund performance table on page 10 for information about the calculation of fund performance.

Terms and definitions

Important terms

Total return shows how the value of the fund’s shares changed over time, assuming you held the shares through the entire period and reinvested all distributions in the fund.

Net asset value (NAV) is the value of all your fund’s assets, minus any liabilities, divided by the number of outstanding shares.

Market price is the current trading price of one share of the fund. Market prices are set by transactions between buyers and sellers on exchanges such as the New York Stock Exchange.

Fixed-income terms

Current rate is the annual rate of return earned from dividends or interest of an investment. Current rate is expressed as a percentage of the price of a security, fund share, or principal investment.

Yield curve is a graph that plots the yields of bonds with equal credit quality against their differing maturity dates, ranging from shortest to longest. It is used as a benchmark for other debt, such as mortgage or bank lending rates.

Comparative indexes

Bloomberg Barclays U.S. Aggregate Bond Index is an unmanaged index of U.S. investment-grade fixed-income securities.

The fund’s blended benchmark is an unmanaged index administered by Putnam Management, 50% of which is the JPMorgan Developed High Yield Index and 50% of which is the ICE BofAML Speculative Grade U.S. Convertible Index.

ICE BofAML (Intercontinental Exchange Bank of America Merrill Lynch) Speculative Grade U.S. Convertible Index is an unmanaged index of U.S. convertible securities.

ICE BofAML U.S. 3-Month Treasury Bill Index is an unmanaged index that seeks to measure the performance of U.S. Treasury bills available in the marketplace.

JPMorgan Developed High Yield Index is an unmanaged index of high-yield fixed-income securities issued in developed countries.

S&P 500 Index is an unmanaged index of common stock performance.

ICE Data Indices, LLC (“ICE BofAML”), used with permission. ICE BofAML permits use of the ICE BofAML indices and related data on an “as is” basis; makes no warranties regarding same; does not guarantee the suitability, quality, accuracy, timeliness, and/or completeness of the ICE BofAML indices or any data included in, related to, or derived therefrom; assumes no liability in connection with the use of the foregoing; and does not sponsor, endorse, or recommend Putnam Investments, or any of its products or services.

Indexes assume reinvestment of all distributions and do not account for fees. Securities and performance of a fund and an index will differ. You cannot invest directly in an index.

Lipper is a third-party industry-ranking entity that ranks mutual funds. Its rankings do not reflect sales charges. Lipper rankings are based on total return at net asset value relative to other funds that have similar current investment styles or objectives as determined by Lipper. Lipper may change a fund’s category assignment at its discretion. Lipper category averages reflect performance trends for funds within a category.

Other information for shareholders

Important notice regarding share repurchase program

In September 2017, the Trustees of your fund approved the renewal of a share repurchase program that had been in effect since 2005. This renewal allows your fund to repurchase, in the 12 months beginning October 10, 2017, up to 10% of the fund’s common shares outstanding as of October 9, 2017.

Important notice regarding delivery of shareholder documents

In accordance with Securities and Exchange Commission (SEC) regulations, Putnam sends a single copy of annual and semiannual shareholder reports, prospectuses, and proxy statements to Putnam shareholders who share the same address, unless a shareholder requests otherwise. If you prefer to receive your own copy of these documents, please call Putnam at 1-800-225-1581, and Putnam will begin sending individual copies within 30 days.

Proxy voting

Putnam is committed to managing our mutual funds in the best interests of our shareholders. The Putnam funds’ proxy voting guidelines and procedures, as well as information regarding how your fund voted proxies relating to portfolio securities during the 12-month period ended June 30, 2017, are available in the Individual Investors section of putnam.com, and on the SEC’s website, www.sec.gov. If you have questions about finding forms on the SEC’s website, you may call the SEC at 1-800-SEC-0330. You may also obtain the Putnam funds’ proxy voting guidelines and procedures at no charge by calling Putnam’s Shareholder Services at 1-800-225-1581.

Fund portfolio holdings

The fund will file a complete schedule of its portfolio holdings with the SEC for the first and third quarters of each fiscal year on Form N-Q. Shareholders may obtain the fund’s Form N-Q on the SEC’s website at www.sec.gov. In addition, the fund’s Form N-Q may be reviewed and copied at the SEC’s Public Reference Room in Washington, D.C. You may call the SEC at 1-800-SEC-0330 for information about the SEC’s website or the operation of the Public Reference Room.

Trustee and employee fund ownership

Putnam employees and members of the Board of Trustees place their faith, confidence, and, most importantly, investment dollars in Putnam mutual funds. As of February 28, 2018, Putnam employees had approximately $528,000,000 and the Trustees had approximately $81,000,000 invested in Putnam mutual funds. These amounts include investments by the Trustees’ and employees’ immediate family members as well as investments through retirement and deferred compensation plans.

Summary of Putnam Closed-End Funds’ Amended and Restated Dividend Reinvestment Plans

Putnam High Income Securities Fund, Putnam Managed Municipal Income Trust, Putnam Master Intermediate Income Trust, Putnam Municipal Opportunities Trust and Putnam Premier Income Trust (each, a “Fund” and collectively, the “Funds”) each offer a dividend reinvestment plan (each, a “Plan” and collectively, the “Plans”). If you participate in a Plan, all income dividends and capital gain distributions are automatically reinvested in Fund shares by the Fund’s agent, Putnam Investor Services, Inc. (the “Agent”). If you are not participating in a Plan, every month you will receive all dividends and other distributions in cash, paid by check and mailed directly to you.

Upon a purchase (or, where applicable, upon registration of transfer on the shareholder records of a Fund) of shares of a Fund by a registered shareholder, each such shareholder will be deemed to have elected to participate in that Fund’s Plan. Each such shareholder will have all distributions by a Fund automatically reinvested in additional shares, unless such shareholder elects to terminate participation in a Plan by instructing the Agent to pay future distributions in cash. Shareholders who were not participants in a Plan as of January 31, 2010, will continue to receive distributions in cash but may enroll in a Plan at any time by contacting the Agent.

If you participate in a Fund’s Plan, the Agent will automatically reinvest subsequent distributions, and the Agent will send you a confirmation in the mail telling you how many additional shares were issued to your account.

To change your enrollment status or to request additional information about the Plans, you may contact the Agent either in writing, at P.O. Box 8383, Boston, MA 02266-8383, or by telephone at 1-800-225-1581 during normal East Coast business hours.

How you acquire additional shares through a Plan If the market price per share for your Fund’s shares (plus estimated brokerage commissions) is greater than or equal to their net asset value per share on the payment date for a distribution, you will be issued shares of the Fund at a value equal to the higher of the net asset value per share on that date or 95% of the market price per share on that date.

If the market price per share for your Fund’s shares (plus estimated brokerage commissions) is less than their net asset value per share on the payment date for a distribution, the Agent will buy Fund shares for participating accounts in the open market. The Agent will aggregate open-market purchases on behalf of all participants, and the average price (including brokerage commissions) of all shares purchased by the Agent will be the price per share allocable to each participant. The Agent will generally complete these open-market purchases within five business days following the payment date. If, before the Agent has completed open-market purchases, the market price per share (plus estimated brokerage commissions) rises to exceed the net asset value per share on the payment date, then the purchase price may exceed the net asset value per share, potentially resulting in the acquisition of fewer shares than if the distribution had been paid in newly issued shares.

How to withdraw from a Plan Participants may withdraw from a Fund’s Plan at any time by notifying the Agent, either in writing or by telephone. Such withdrawal will be effective immediately if notice is received by the Agent with sufficient time prior to any distribution record date; otherwise, such withdrawal will be effective with respect to any subsequent distribution following notice of withdrawal. There is no penalty for withdrawing from or not participating in a Plan.

Plan administration The Agent will credit all shares acquired for a participant under a Plan to the account in which the participant’s common shares are held. Each participant will

be sent reasonably promptly a confirmation by the Agent of each acquisition made for his or her account.

About brokerage fees Each participant pays a proportionate share of any brokerage commissions incurred if the Agent purchases additional shares on the open market, in accordance with the Plans. There are no brokerage charges applied to shares issued directly by the Funds under the Plans.

About taxes and Plan amendments Reinvesting dividend and capital gain distributions in shares of the Funds does not relieve you of tax obligations, which are the same as if you had received cash distributions. The Agent supplies tax information to you and to the IRS annually. Each Fund reserves the right to amend or terminate its Plan upon 30 days’ written notice. However, the Agent may assign its rights, and delegate its duties, to a successor agent with the prior consent of a Fund and without prior notice to Plan participants.

If your shares are held in a broker or nominee name If your shares are held in the name of a broker or nominee offering a dividend reinvestment service, consult your broker or nominee to ensure that an appropriate election is made on your behalf. If the broker or nominee holding your shares does not provide a reinvestment service, you may need to register your shares in your own name in order to participate in a Plan.

In the case of record shareholders such as banks, brokers or nominees that hold shares for others who are the beneficial owners of such shares, the Agent will administer the Plan on the basis of the number of shares certified by the record shareholder as representing the total amount registered in such shareholder’s name and held for the account of beneficial owners who are to participate in the Plan.

Financial statements

These sections of the report, as well as the accompanying Notes, constitute the fund’s financial statements.

The fund’s portfolio lists all the fund’s investments and their values as of the last day of the reporting period. Holdings are organized by asset type and industry sector, country, or state to show areas of concentration and diversification.

Statement of assets and liabilities shows how the fund’s net assets and share price are determined. All investment and non-investment assets are added together. Any unpaid expenses and other liabilities are subtracted from this total. The result is divided by the number of shares to determine the net asset value per share. (For funds with preferred shares, the amount subtracted from total assets includes the liquidation preference of preferred shares.)

Statement of operations shows the fund’s net investment gain or loss. This is done by first adding up all the fund’s earnings — from dividends and interest income — and subtracting its operating expenses to determine net investment income (or loss). Then, any net gain or loss the fund realized on the sales of its holdings — as well as any unrealized gains or losses over the period — is added to or subtracted from the net investment result to determine the fund’s net gain or loss for the fiscal period.

Statement of changes in net assets shows how the fund’s net assets were affected by the fund’s net investment gain or loss, by distributions to shareholders, and by changes in the number of the fund’s shares. It lists distributions and their sources (net investment income or realized capital gains) over the current reporting period and the most recent fiscal year-end. The distributions listed here may not match the sources listed in the Statement of operations because the distributions are determined on a tax basis and may be paid in a different period from the one in which they were earned. Dividend sources are estimated at the time of declaration. Actual results may vary. Any non-taxable return of capital cannot be determined until final tax calculations are completed after the end of the fund’s fiscal year.

Financial highlights provide an overview of the fund’s investment results, per-share distributions, expense ratios, net investment income ratios, and portfolio turnover in one summary table, reflecting the five most recent reporting periods. In a semiannual report, the highlights table also includes the current reporting period.

The fund’s portfolio 2/28/18 (Unaudited)