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UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , DC 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 OR □ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO Delaware ( State or other jurisdiction of incorporation or organization ) Title of each class Common Stock , par value $ 0.01 NBT BANCORP INC . ( Exact name of registrant as specified in its charter ) per COMMISSION FILE NUMBER : 0-14703 52 SOUTH BROAD STREET , NORWICH , NEW YORK 13815 ( Address of principal executive office ) ( Zip Code ) ( Registrant's telephone number , including area code ) ( 607 ) 337-2265 Securities registered pursuant to section 12 ( b ) of the Act : Trading Symbol ( s ) . NBTB share 16-1268674 ( I.R.S. Employer Identification No. ) 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 Accelerated filer 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 and post such files ) . Yes No Name of each exchange on which registered The NASDAQ Stock Market LLC 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 > Non - accelerated filer naller reporting company □ Emerging growth 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 . DOCUMENTS INCORPORATED BY REFERENCE 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 . Yes - No Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes No Based on the closing price of the registrant's common stock as of June 30 , 2020 , the aggregate market value of the voting stock , common stock , par value , $ 0.01 per share , held by non - affiliates of the registrant is $ 1,302,040,742 . The number of shares of common stock outstanding as of February 8 , 2021 , was 43,581,317 . Portions of the registrant's definitive Proxy Statement for its Annual Meeting of Stockholders to be held on May 25 , 2021 are incorporated by reference into Part III , Items 10 , 11 , 12 , 13 and 14 of this Form 10 - K .