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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 Commission file number 0-18082 GREAT SOUTHERN BANCORP , INC . ( Exact name of registrant as specified in its charter ) Maryland ( State or other jurisdiction of incorporation or organization ) 1451 E. Battlefield , Springfield , Missouri ( Address of principal executive offices ) 43-1524856 Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common Stock , par value $ 0.01 per share ( I.R.S. Employer Identification No. ) ( 417 ) 887-4400 Registrant's telephone number , including area code 65804 ( Zip Code ) Trading Symbol ( s ) Name of each exchange on which registered GSBC The NASDAQ Stock Market LLC Securities registered pursuant to Section 12 ( g ) of the Act : None . Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes No Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes > No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes > No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See the definitions of " large accelerated filer " , " accelerated filer , " " smaller reporting company " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer Accelerated filer > Non - accelerated filer company If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Smaller reporting company Emerging growth Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Indicated by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes No The aggregate market value of the common stock of the registrant held by non - affiliates of the Registrant on June 30 , 2020 , computed by reference to the closing price of such shares on that date , was $ 438,764,780 . At March 2 , 2021 , 13,690,119 shares of the Registrant's common stock were outstanding .