Summary Prospectus by Investment Company - Form 497K

September 30, 2024

SUMMARY PROSPECTUS

SIIT Large Cap Disciplined Equity Fund (SCPAX)

Class A

Before you invest, you may want to review the Fund's Prospectus, which contains information about the Fund and its risks. You can find the Fund's Prospectus and other information about the Fund, including the Fund's Statement of Additional Information and annual and semi-annual reports, online at seic.com/fundprospectuses. You can also get this information at no cost by dialing 1-800-DIAL-SEI. The Fund's Prospectus and Statement of Additional Information, dated September 30, 2024, as may be supplemented from time to time, are incorporated by reference into this Summary Prospectus and may be obtained, free of charge, at the website or phone number noted above.

seic.com

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Investment Goal

Capital appreciation.

Fees and Expenses

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

ANNUAL FUND OPERATING EXPENSES

EXAMPLE

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

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual Fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 137% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Large Cap Disciplined Equity Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of large companies. These securities may include common stocks, preferred stocks, depositary receipts, warrants, exchange-traded funds (ETFs) and real estate investment trusts (REITs) based on a large capitalization equity index and equity securities of foreign companies. The Fund will invest primarily in common stocks of U.S. companies with market capitalizations in the range of companies in the S&P 500 Index (between $7.0 billion and $3.4 trillion as of July 31, 2024) at the time of purchase. The market capitalization range and the composition of the S&P 500 Index are subject to change. The Fund may also, to a lesser extent, invest in common and preferred stocks of small capitalization companies.

The Fund seeks to exceed the total return of the S&P 500 Index, with a similar level of volatility, by investing primarily in a portfolio of common stocks included in the S&P 500 Index, as well as other equity investments and derivative instruments whose value is derived from the performance of the S&P 500 Index. The Fund uses a multi-manager approach, relying on one or more sub-advisers (each, a Sub-Adviser and collectively, the Sub-Advisers) with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SEI Investments Management Corporation (SIMC or the Adviser). The Fund may employ Sub-Advisers that use a variety of different methods to seek to outperform the Fund's benchmark, including purchasing stocks with strong anticipated future earnings growth, selecting stocks that the Sub-Adviser believes are undervalued relative to their fundamentals, capturing returns from the natural volatility of the market and employing strategies that rotate among various sectors of the market. The Fund may also utilize one or more additional Sub-Advisers who manage in a complementary style with the objective to seek to add value over the S&P 500 Index while maintaining a similar level of volatility to the S&P 500 Index. Due to its investment strategy, the Fund may buy and sell securities frequently.

One or more Sub-Adviser(s) may implement a long/short equity investment strategy by investing in securities believed to offer capital appreciation opportunities while also attempting to take advantage of an anticipated decline in the price of a company. A long/short equity investment strategy takes (i) long positions with respect to investments that the Sub-Adviser believes to be undervalued relative to their potential increase in price, and (ii) short positions (including through derivatives instruments such as swaps) with respect to investments that the Sub-Adviser believes to be overvalued and likely to decrease in price. A long/short

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equity investment strategy seeks returns from strong security selection on both the long and short sides. These long and short positions may be completely unrelated.

Principal Risks

Market Risk - The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

Large Capitalization Risk - The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

Investment Style Risk - The risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. Sub-Adviser(s) may exhibit poor security selection, losing money on both the long and short sides.

Preferred Stock Risk - Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

Depositary Receipts Risk - Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

Warrants Risk - Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

Exchange-Traded Funds Risk - The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF's expenses.

Foreign Investment Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries.

Currency Risk - As a result of the Fund's investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund's investments in securities denominated in foreign currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

REITs Risk - REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund's investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

Small Capitalization Risk - Smaller capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger companies. Small capitalization stocks may be traded

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over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

Short Sales Risk - A short sale involves the sale of a security that the Fund does not own in the expectation of purchasing the same security (or a security exchangeable therefore) at a later date at a lower price. Short sales expose the Fund to the risk that it will be required to buy the security sold short (also known as "covering" the short position) at a time when the security has appreciated in value, thus resulting in a loss to the Fund. Investment in short sales may also cause the Fund to incur expenses related to borrowing securities. Reinvesting proceeds received from short selling may create leverage, which can amplify the effects of market volatility on the Fund's share price. In addition, shorting a future contract may require posting only a margin that may amount to less than the notional exposure of the contract. Such a practice may exacerbate the loss in a case of adverse price action.

Derivatives Risk - The Fund's use of futures contracts and swaps is subject to leverage risk, correlation risk, liquidity risk and market risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund's use of swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund's initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund's use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

Liquidity Risk - The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

Leverage Risk - The Fund's use of derivatives may result in the Fund's total investment exposure substantially exceeding the value of its portfolio securities and the Fund's investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund's share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund's use of leverage may result in a heightened risk of investment loss.

Credit Risk - The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

Portfolio Turnover Risk - Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund's performance.

Investing in the Fund involves risk, and there is no guarantee that the Fund will achieve its investment goal. You could lose money on your investment in the Fund, just as you could with other investments. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance Information

The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten calendar years, and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception compare with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.

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Average Annual Total Returns (for the periods ended December 31, 2023)

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

Management

Investment Adviser and Portfolio Managers. SEI Investments Management Corporation

Sub-Advisers and Portfolio Managers.

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Purchase and Sale of Fund Shares

The Fund's minimum investment requirements for Class A Shares are: (a) that you must be an Eligible Investor (i.e., institutions or other SIMC advisory clients that have entered into an investment management agreement with SIMC or institutional investors, employee benefit plans and other similar entities purchasing through approved intermediaries); and (b) that your minimum initial investment must be $100,000, with minimum subsequent investments of $1,000, which may be waived at the discretion of SIMC. You may purchase and redeem shares of the Fund on any day that the New York Stock Exchange (NYSE) is open for business (a Business Day). You may sell your Fund shares by contacting your authorized financial institution or intermediary directly. Authorized financial institutions and intermediaries may redeem Fund shares on behalf of their clients by contacting the Fund's transfer agent (the Transfer Agent) or the Fund's authorized agent, using certain SEI Investments Company (SEI) or third party systems or by calling 1-800-858-7233, as applicable.

Tax Information

The distributions made by the Fund are generally taxable and will be taxed as qualified dividend income, ordinary income or capital gains. If you are investing through a tax-deferred arrangement, such as a 401(k) plan or individual retirement account, you will generally not be subject to federal taxation on Fund distributions until you begin receiving distributions from your tax-deferred arrangement. You should consult your tax advisor regarding the rules governing your tax-deferred arrangement.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase Fund shares through a broker-dealer or other financial intermediary, such as a bank, the Fund and its related companies may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.