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UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C. 20549 FORM 10 - K ( Mark One ) ✓ ☐ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number 001-34095 FIRST BUSINESS FINANCIAL SERVICES , INC . ( Exact name of registrant as specified in its charter ) Wisconsin ( State or other jurisdiction of incorporation or organization ) 401 Charmany Drive , Madison , WI ( Address of principal executive offices ) 39-1576570 ( I.R.S. Employer Identification No. ) Registrant's telephone number , including area code : ( 608 ) 238-8008 53719 ( Zip Code ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common Stock , $ 0.01 par value Trading Symbol ( s ) FBIZ Name of each exchange on which registered The Nasdaq Stock Market LLC Securities registered pursuant to Section 12 ( g ) of the Act None No þ Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes ¨ Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . Yes " No p 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 þ 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 during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files . ) Yes þ 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 . ( Check one ) : Large accelerated filer ☐ Accelerated filer ✓ Non - accelerated filer □ Smaller reporting company ✓ Emerging growth company ㅁ 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 . 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 . þ Indicate 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 equity held by non - affiliates computed by reference to the closing price of such common equity , as of the last business day of the registrant's most recently completed second fiscal quarter , was approximately $ 140.3 million . As of February 22 , 2021 , 8,511,536 shares of common stock were outstanding . DOCUMENTS INCORPORATED BY REFERENCE Part III - Portions of the Proxy Statement for the Annual Meeting of Shareholders to be held on April 30 , 2021 are incorporated by reference into Part III hereof .