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    <ACCEPTANCE-DATETIME>20211112111913
    ACCESSION NUMBER:		0000350894-21-000063
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		17
    CONFORMED PERIOD OF REPORT:	20211112
    ITEM INFORMATION:		Regulation FD Disclosure
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20211112
    DATE AS OF CHANGE:		20211112

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			SEI INVESTMENTS CO
    		CENTRAL INDEX KEY:			0000350894
    		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
    		IRS NUMBER:				231707341
    		STATE OF INCORPORATION:			PA
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	000-10200
    		FILM NUMBER:		211401485

    	BUSINESS ADDRESS:
    		STREET 1:		1 FREEDOM VALLEY DRIVE
    		CITY:			OAKS
    		STATE:			PA
    		ZIP:			19456-1100
    		BUSINESS PHONE:		6106761000

    	MAIL ADDRESS:
    		STREET 1:		1 FREEDOM VALLEY DRIVE
    		CITY:			OAKS
    		STATE:			PA
    		ZIP:			19456-1100

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	SEI INVESTMENT CO
    		DATE OF NAME CHANGE:	20040806

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	SEI CORP
    		DATE OF NAME CHANGE:	19920703
    </SEC-HEADER>
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    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>seic-20211112.htm
    <DESCRIPTION>FORM 8-K
    <TEXT>
    Document 1 - file: seic-20211112.htm

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    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>2
    <FILENAME>novusrls111221.htm
    <DESCRIPTION>PRESS RELEASE
    <TEXT>
    Document 2 - file: novusrls111221.htm

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    <SEQUENCE>3
    <FILENAME>seic-20211112.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
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    <FILENAME>novusrls111221001.jpg
    <DESCRIPTION>GRAPHIC
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    <SEQUENCE>11
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    <DOCUMENT>
    <TYPE>EXCEL
    <SEQUENCE>12
    <FILENAME>Financial_Report.xlsx
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    Document 12 - file: Financial_Report.xlsx

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    <TYPE>XML
    <SEQUENCE>13
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    <TYPE>XML
    <SEQUENCE>15
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    <TYPE>JSON
    <SEQUENCE>17
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    <TEXT>
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