    <SEC-DOCUMENT>0000355811-21-000003-index.html : 20210129
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    <ACCEPTANCE-DATETIME>20210129075957
    ACCESSION NUMBER:		0000355811-21-000003
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		16
    CONFORMED PERIOD OF REPORT:	20210129
    ITEM INFORMATION:		Results of Operations and Financial Condition
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20210129
    DATE AS OF CHANGE:		20210129

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			GENTEX CORP
    		CENTRAL INDEX KEY:			0000355811
    		STANDARD INDUSTRIAL CLASSIFICATION:	MOTOR VEHICLE PARTS & ACCESSORIES [3714]
    		IRS NUMBER:				382030505
    		STATE OF INCORPORATION:			MI
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	000-10235
    		FILM NUMBER:		21568210

    	BUSINESS ADDRESS:
    		STREET 1:		600 N CENTENNIAL ST
    		CITY:			ZEELAND
    		STATE:			MI
    		ZIP:			49464
    		BUSINESS PHONE:		6167721800

    	MAIL ADDRESS:
    		STREET 1:		600 N CENTENNIAL STREET
    		CITY:			ZEELAND
    		STATE:			MI
    		ZIP:			49464
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    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>gntx-20210129.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: gntx-20210129.htm

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    <FILENAME>exhibit99112312020.htm
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    <TYPE>EX-101.SCH
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    <FILENAME>gntx-20210129.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
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    <FILENAME>gntx-20210129_cal.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION CALCULATION LINKBASE DOCUMENT
    <TEXT>
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    <TYPE>EXCEL
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    <FILENAME>Financial_Report.xlsx
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    <TEXT>
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    <TYPE>ZIP
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