September 30, 2021

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

The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time.

Please remember that past performance is not necessarily an indication of future results

putnam.com

Year-to-date performance through

Jun. 30, 2020

(9.91%)

Best calendar quarter

Sep. 30, 2016

4.14%

Worst calendar quarter

Mar. 31, 2016

(3.95%)

After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes.

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown.

Fees and expenses

The following tables describe the fees and expenses you may pay if you buy and hold Class I shares of the fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	Fund summary C 000152757 [Member]
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	none
Maximum Deferred Sales Charge (as a percentage)	none

Example

The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. Only the first year of each period in the example takes into account the expense reimbursement described above. Your actual costs may be higher or lower.

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years	Portfolio Turnover, Rate	Risk Lose Money [Text]
Fund summary | C 000152757 [Member] | USD ($)	49	202	368	850	1311.00%	It is important to understand that you can lose money by investing in the fund.

Portfolio turnover

The fund pays transaction-related costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher turnover rate may indicate higher transaction costs and may result in higher taxes when the fund’s shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or the above example, affect fund performance. The fund’s turnover rate in the most recent fiscal year was 1,311%.

Risks

It is important to understand that you can lose money by investing in the fund.

The value of investments in the fund’s portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general economic, political or financial market conditions, investor sentiment and market perceptions, government actions, geopolitical events or changes, and factors related to a specific issuer, geography, industry or sector, such as the housing or real estate markets. These and other factors may lead to increased volatility and reduced liquidity in the fund’s portfolio holdings or in relevant markets. The risks associated with bond investments include interest rate risk, which means the value of the fund’s investments is likely to fall if interest rates rise.

Bond investments are also subject to credit risk, which is the risk that the issuers of the fund’s investments may default on payment of interest or principal. Default risk is generally higher for non-qualified mortgages. Interest rate risk is generally greater for longer-term bonds, and credit risk is generally greater for below-investment grade bonds, which may be considered speculative. Mortgage- and asset-backed investments, unlike traditional debt investments, are also subject to prepayment risk, which means that they may increase in value less than other bonds when interest rates decline and decline in value more than other bonds when interest rates rise. We may have to invest the proceeds from prepaid investments, including mortgage- and asset-backed investments, in other investments with less attractive terms and yields. The fund’s investments in mortgage-backed securities and asset-backed securities, and in certain other securities and derivatives, may be or become illiquid. The fund’s concentration in an industry group composed of privately issued residential and commercial mortgage-backed securities and mortgage-backed securities issued or guaranteed by the U.S. government or its agencies or instrumentalities may make the fund’s net asset value more susceptible to economic, market, political and other developments affecting the residential and commercial real estate markets and the servicing of mortgage loans secured by real estate properties. During periods of difficult economic conditions, delinquencies and losses on commercial mortgage-backed securities in particular generally increase, including as a result of the effects of those conditions on commercial real estate markets, the ability of commercial tenants to make loan payments, and the ability of a property to attract and retain commercial tenants.

Our use of derivatives may increase the risks of investing in the fund by increasing investment exposure (which may be considered leverage) or, in the case of many over-the-counter instruments, because of the potential inability to terminate or sell derivatives positions and the potential failure of the other party to the instrument to meet its obligations.

4          Prospectus

The fund expects to engage in frequent trading. Funds with high turnover may be more likely to realize capital gains that must be distributed to shareholders as taxable income and may incur higher transaction costs than funds with relatively lower turnover, which may detract from performance.

There is no guarantee that the investment techniques, analyses, or judgments that we apply in making investment decisions for the fund will produce the intended outcome or that the investments we select for the fund will perform as well as other securities that were not selected for the fund. We, or the fund’s other service providers, may experience disruptions or operating errors that could negatively impact the fund.

The fund may not achieve its goal, and it is not intended to be a complete investment program. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance

The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time. Please remember that past performance is not necessarily an indication of future results. Monthly performance figures for the fund are available at putnam.com/institutional.

Investments, risks, and performance

Investments

We invest mainly in mortgage-related fixed income securities and related derivatives that are either investment-grade or below-investment-grade in quality (sometimes referred to as “junk bonds”). Under normal circumstances, we invest at least 80% of the fund’s net assets in mortgages, mortgage-related fixed income securities and related derivatives (i.e., derivatives used to acquire exposure to, or whose underlying securities are, mortgages or mortgage-related securities). The fund generally uses the net unrealized gain or loss, or market value, of mortgage-related derivatives for purposes of this policy, but may use the notional value of a derivative if that is determined to be a more appropriate measure of the fund’s investment exposure. This policy may be changed only after 60 days’ notice to shareholders.

We expect to invest in lower-rated, higher-yielding mortgage-backed securities, including non-agency residential mortgage-backed securities (which may be backed by non-qualified or “sub-prime” mortgages), commercial mortgage-backed securities, collateralized mortgage obligations (including interest only, principal only, and other prepayment derivatives), and agency mortgage-backed securities. The fund currently has significant investment exposure to commercial mortgage-backed securities. Non-agency (i.e., privately issued) securities typically are lower-rated and higher yielding than securities issued or backed by agencies such as Ginnie Mae, Fannie Mae or Freddie Mac. While our emphasis will be on mortgage-backed securities, we may also invest to a lesser extent in other types of asset-backed securities. We may consider, among other factors, credit, interest rate, prepayment and liquidity risks, as well as general market conditions, when deciding whether to buy or sell

Prospectus          3

investments. We typically use to a significant extent derivatives, including interest rate swaps, forward delivery contracts and total return swaps, options and swaptions on mortgage-backed securities and indices, for both hedging and non-hedging purposes, including to obtain or adjust exposure to mortgage-backed investments.

Annual total returns for class I shares  

Average annual total returns (for periods ended 12/31/19)