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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 or 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 : 1-31398 NATURAL GAS SERVICES GROUP , INC . ( Exact Name of Registrant as Specified in its Charter ) Colorado ( State or other jurisdiction of incorporation or organization ) 404 Veterans Airpark Lane , Suite 300 , Midland , Texas ( Address of principal executive offices ) Registrant's telephone number , including area code : Title of each class Common Stock , $ .01 par value Securities registered pursuant to section 12 ( g ) of the Act : None . Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) NGS Large accelerated filer ( I.R.S. Employer Identification No. ) 75-2811855 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 and posted on its corporate Web site , if any , every Interactive Data File to be submitted and posted pursuant to Rule 405 of Regulation S - T ( §40232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit and post such files ) . Accelerated filer 79705 ( Zip Code ) ( 432 ) 262-2700 Name of each exchange on which registered New York Stock Exchange Yes > No Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S - K is not contained herein , and will not be contained , to the best of registrant's knowledge , in definitive proxy or information statements incorporated by reference in Part III of this Form 10 - K or any amendment to this Form 10 - K . Yes No X Non - accelerated filer > Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , or a smaller reporting company . See definition of " accelerated filer and large accelerated filer " in Rule 12b - 2 of the Exchange Act . ( Check one ) : Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes No > Smaller 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 . The aggregate market value of voting and non - voting common equity held by non - affiliates of the Registrant as of June 30 , 2020 was approximately $ 82,414,178 based on the closing price of the common stock on that date on the New York Stock Exchange . At March 26 , 2021 , there were 13,605,803 shares of the Registrant's common stock outstanding . Documents incorporated by reference Certain information called for in Items 10 , 11 , 12 , 13 and 14 of Part III are incorporated by reference to the registrant's definitive proxy statement for the annual meeting of shareholders expected to be held on June 17 , 2021 .