|         |                                                                                      |  |  |  |  |
|---------|--------------------------------------------------------------------------------------|--|--|--|--|
| ☒ | ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

|         |                                                                                          |  |  |  |  |
|---------|------------------------------------------------------------------------------------------|--|--|--|--|
| ☐ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |

|                                                              |        |                                    |  |  |  |  |  |  |
|--------------------------------------------------------------|--------|------------------------------------|--|--|--|--|--|--|
| Pennsylvania                                                 |   | 23-1707341                         |
| State or Other Jurisdiction of Incorporation or Organization |   | I.R.S. Employer Identification No. |

|                                        |        |                |  |                                           |  |  |  |  |  |  |  |  |  |  |
|----------------------------------------|--------|----------------|--|-------------------------------------------|--|--|--|--|--|--|--|--|--|--|
| Title of each class                    |   | Trading Symbol |  | Name of each exchange on which registered |
| Common Stock, par value $.01 per share |   | SEIC           |  | The NASDAQ Stock Market LLC               |
|                                        |        |                |  | (The NASDAQ Global Select Market®)   |

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|                         |         |  |                                     |         |  |  |  |  |  |  |  |  |  |  |
|-------------------------|---------|--|-------------------------------------|---------|--|--|--|--|--|--|--|--|--|--|
| Large accelerated filer | ☒ |  | Accelerated filer              | ☐ |
|                         |         |  |                                     |         |
| Non-accelerated filer   | ☐ |  | Smaller reporting company | ☐ |
|                         |         |  |                                     |         |
| Emerging growth company | ☐ |  |                                     |         |

|                              |        |             |  |  |  |  |  |  |
|------------------------------|--------|-------------|--|--|--|--|--|--|
|                              |        |             |
| Common Stock, $.01 par value |   | 131,352,305 |

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|                           |                                                                                                                                                                                                                              |  |  |  |  |
|---------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--|--|--|--|
|                           |                                                                                                                                                                                                                              |
| (a) (1) and (2) | Financial Statements and Financial Statement Schedules. The following is a list of the Consolidated Financial Statements of the Company and its subsidiaries and supplementary data filed as part of Item 8 hereof: |
|                           |                                                                                                                                                                                                                              |
|                           | Reports of Independent Registered Public Accounting Firm                                                                                                                                                                     |
|                           | Consolidated Balance Sheets — December 31, 2023 and 2022                                                                                                                                                               |
|                           | Consolidated Statements of Operations — For the years ended December 31, 2023, 2022 and 2021                                                                                                                           |
|                           | Consolidated Statements of Comprehensive Income — For the years ended December 31, 2023, 2022 and 2021                                                                                                                 |
|                           | Consolidated Statements of Changes in Equity — For the years ended December 31, 2023, 2022 and 2021                                                                                                                    |
|                           | Consolidated Statements of Cash Flows — For the years ended December 31, 2023, 2022 and 2021                                                                                                                           |
|                           | Notes to Consolidated Financial Statements                                                                                                                                                                                   |
|                           | Schedule II - Valuation and Qualifying Accounts and Reserves — For the years ended December 31, 2023, 2022 and 2021                                                                                                    |
|                           | All other schedules are omitted because they are not applicable, or not required, or because the required information is included in the Consolidated Financial Statements or notes thereto.                                 |
| (a) (3)                   | Exhibits, Including Those Incorporated by Reference. The exhibits to this Report are listed on the accompanying index to exhibits and are incorporated herein by reference or are filed as part of this Amendment No. 1.     |

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|        |        |              |                                                                                                                                                                                                                                                                                                                                                          |  |  |  |  |  |  |  |  |
|--------|--------|--------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--|--|--|--|--|--|--|--|
| 3.1    | (P)    |    | Articles of Incorporation of the Registrant as amended on January 21, 1983. (Incorporated by reference to exhibit 3.1 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 1982.)                                                                                                                       |
| 3.1.2  | (P)    |    | Amendment to Articles of Incorporation of the Registrant, dated May 21, 1992. (Incorporated by reference to exhibit 3.1.2 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 1992.)                                                                                                                   |
| 3.1.3  | (P)    |    | Amendment to Articles of Incorporation of the Registrant, dated May 26, 1994. (Incorporated by reference to exhibit 3.1.3 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 1994.)                                                                                                                   |
| 3.1.4  | (P)    |    | Amendment to Articles of Incorporation of the Registrant, dated November 21, 1996. (Incorporated by reference to exhibit 3.1.4 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 1996.)                                                                                                              |
| 3.1.5  |        |    | Amendment to Articles of Incorporation of the Registrant, dated February 14, 2001. (Incorporated by reference to exhibit 3.1.5 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2000.)                                                                                                              |
| 3.2    |        |    | Amended and Restated By-Laws. (Incorporated by reference to exhibit 99.3 to the Registrant’s Current Report on Form 8-K dated March 31, 2022.)                                                                                                                                                                                                     |
| 4.2    |        |    | Statement with Respect to Shares of a Domestic Corporation amending the designations of Series A Junior Participating Preferred Shares as a series of the Series Preferred Stock of the Company, dated January 6, 2009. (Incorporated by reference to exhibit 3.1 to the Registrant’s Current Report on Form 8-K dated January 6, 2009.) |
|        |        |              |
|        |        |    | Note: Exhibits 10.1 through 10.13 constitute the management contracts and executive compensatory plans or arrangements in which certain of the directors and executive officers of the Registrant participate.                                                                                                                                       |
|        |        |              |
| 10.1   |        |              | 2014 Omnibus Equity Compensation Plan Restricted Stock Unit Agreement. (Incorporated by reference to exhibit 10.1 to the Registrant's Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2022.)                                                                                                                                       |
| 10.2   |   |              | 2014 Omnibus Equity Compensation Plan Stock Option Grant Agreement. (Incorporated by reference to exhibit 10.2 to the Registrant's Annual Report on Form 10-K for the fiscal year ended December 31, 2022.)                                                                                                                                              |
| 10.4   |        |    | 1998 Equity Compensation Plan, Amended and Restated as of April 8, 2003. (Incorporated by reference to exhibit 99.1 to the Registrant’s Registration Statement on Form S-8 (No. 333-111224) filed December 16, 2003.)                                                                                                                    |
| 10.4.1 |        |    | Amendment 2006-1 to the 1998 Equity Compensation Plan, Amended and Restated as of April 8, 2003. (Incorporated by reference to exhibit 10.4.1 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2006.)                                                                                               |
| 10.5   | *      |    | Employee Stock Purchase Plan as Amended and Restated on April 21, 2020.                                                                                                                                                                                                                                                                                  |
| 10.6   |        |    | SEI Capital Accumulation Plan. (Incorporated by reference to exhibit 99(e) to the Registrant’s Registration Statement on Form S-8 (No. 333-41343) filed December 2, 1997.)                                                                                                                                                                    |
| 10.10  |        |    | 2007 Equity Compensation Plan. (Incorporated by reference to exhibit 10.10 to the Registrant’s Current Report on Form 8-K dated April 11, 2007.)                                                                                                                                                                                              |
| 10.11  |        |              | 2014 Omnibus Equity Compensation Plan. (Incorporated by reference to exhibit 10.11 to the Registrant’s Current Report on Form 8-K dated May 21, 2014.)                                                                                                                                                                                             |
| 10.12  |        |              | Employment Agreement, dated May 2, 2018, between Michael N. Peterson and the Registrant. (Incorporated by reference to exhibit 10.12 to the Registrant's Annual Report on Form 10-K for the fiscal year ended December 31, 2018.)                                                                                                                        |
| 10.13  |        |              | Employment Agreement, dated March 31, 2022, between Ryan Hicke and the Registrant. (Incorporated by reference to exhibit 99.1 to the Registrant's Current Report on Form 8-K dated March 31, 2022.)                                                                                                                                                      |
| 10.14  |        |              | Employment Agreement, dated January 16, 2024, between Sean Denham and the Registrant. (Incorporated by reference to exhibit 99.1 to the Registrant's Current Report on Form 8-K dated January 16, 2024.)                                                                                                                                                 |

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|         |        |              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |  |  |  |  |  |  |  |  |
|---------|--------|--------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--|--|--|--|--|--|--|--|
| 10.14.1 |        |              | Amendment No. 1 to Employment Agreement, dated January 31, 2024, between Sean Denham and the Registrant. (Incorporated by reference to exhibit 99.2 to the Registrant's Current Report on Form 8-K dated January 16, 2024.)                                                                                                                                                                                                                                                                           |
| 10.22   |        |    | Credit Facility, dated January 14, 2003 between Royal Bank of Canada and SEI Investments Canada Company, a subsidiary of SEI Investments Company. (Incorporated by reference to exhibit 10.22 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2005.)                                                                                                                                                                                            |
| 10.22.1 |        |    | First Amendment, dated June 15, 2005 to Credit Facility, dated January 14, 2003 between Royal Bank of Canada and SEI Investments Canada Company, a subsidiary of SEI Investments Company. (Incorporated by reference to exhibit 10.22.1 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2005.)                                                                                                                                             |
| 10.22.2 |        |    | Second Amendment, dated February 20, 2006 to Credit Facility, dated January 14, 2003 between Royal Bank of Canada and SEI Investments Canada Company, a subsidiary of SEI Investments Company. (Incorporated by reference to exhibit 10.22.2 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2005.)                                                                                                                                        |
| 10.27   |        |              | Credit Agreement, dated as of April 23, 2021 among SEI Investments Company, the Lenders, U.S. Bank National Association, as Syndication Agent, Bank of America, N.A., Citizens Bank, N.A., Manufacturers and Traders Trust Company and Regions Bank, as Documentation Agents, and Wells Fargo Bank, National Association, as Administrative Agent (Incorporated by reference to exhibit 10.27 to the Registrant’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2021.) |
| 10.27.1 |        |              | First Amendment to Credit Agreement dated as of April 17, 2023 among SEI Investments Company, the Lenders, U.S. Bank National Association, as Syndication Agent, Bank of America, N.A., Citizens Bank, N.A., Manufacturers and Traders Trust Company and Regions Bank, as Documentation Agents, and Wells Fargo Bank, National Association, as Administrative Agent (Incorporated by reference to exhibit 10.27.1 to the Registrant's Current Report on Form 8-K dated April 17, 2023.)               |
| 14      |        |    | Code of Ethics for Senior Financial Officers. (Incorporated by reference to exhibit 14 to the Registrant’s Annual Report on Form 10-K for the fiscal year ended December 31, 2003.)                                                                                                                                                                                                                                                                                                        |
| 21      | *      |    | Subsidiaries of the Registrant.                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| 23.1    | *      |    | Consent of KPMG LLP.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| 23.2    | *      |    | Consent of KPMG LLP relating to the financial statements of LSV Asset Management.                                                                                                                                                                                                                                                                                                                                                                                                                     |
| 31.1    |        |    | Rule 13a-15(e)/15d-15(e) Certification of Principal Executive Officer.                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 31.2    |        |    | Rule 13a-15(e)/15d-15(e) Certification of Principal Financial Officer.                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 97      | *      |              | Amended and Restated Compensation Recoupment Policy                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| 99.11   |   |              | Financial Statements of LSV Asset Management dated December 31, 2020 and 2019. (Incorporated by reference to exhibit 99.11 to the Registrant's Annual Report on Form 10-K for the fiscal year ended December 31, 2020.)                                                                                                                                                                                                                                                                               |
| 99.12   |   |              | Financial Statements of LSV Asset Management dated December 31, 2021 and 2020. (Incorporated by reference to exhibit 99.12 to the Registrant's Annual Report on Form 10-K for the fiscal year ended December 31, 2021.)                                                                                                                                                                                                                                                                               |
| 99.13   |   |              | Financial Statements of LSV Asset Management dated December 31, 2022 and 2021. (Incorporated by reference to exhibit 99.13 to the Registrant's Annual Report on Form 10-K for the fiscal year ended December 31, 2022.)                                                                                                                                                                                                                                                                               |
| 99.14   |        |              | Financial Statements of LSV Asset Management dated December 31, 2023 and 2022.                                                                                                                                                                                                                                                                                                                                                                                                                        |
| 101.INS |        |    | XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document.                                                                                                                                                                                                                                                                                                                                       |
| 101.SCH | *      |    | XBRL Taxonomy Extension Schema Document                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| 101.CAL | *      |    | XBRL Taxonomy Extension Calculation Linkbase Document                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| 101.LAB | *      |    | XBRL Taxonomy Extension Label Linkbase Document                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| 101.PRE | *      |    | XBRL Taxonomy Extension Presentation Linkbase Document                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| 101.DEF | *      |    | XBRL Taxonomy Extension Definition Linkbase Document                                                                                                                                                                                                                                                                                                                                                                                                                                                  |

|     |                                                                                                                                         |  |  |  |  |
|-----|-----------------------------------------------------------------------------------------------------------------------------------------|--|--|--|--|
| (P) | Paper Exhibit                                                                                                                           |
| *   | Previously filed with our 2023 Form 10-K, originally filed with the Commission on February 20, 2024, which is being amended hereby |

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|           |                   |        |                         |        |                                 |  |  |  |  |  |  |  |  |  |  |  |  |
|-----------|-------------------|--------|-------------------------|--------|---------------------------------|--|--|--|--|--|--|--|--|--|--|--|--|
|           |                   |        |                         |        |                                 |
|           |                   |   | SEI INVESTMENTS COMPANY |
|           |                   |        |                         |
| Date: | February 22, 2024 |   | By:                 |   | /s/ Dennis J. McGonigle |
|           |                   |   |                         |   | Dennis J. McGonigle             |
|           |                   |   |                         |   | Chief Financial Officer         |