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0 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 001-38600 TENABLE HOLDINGS , INC . ( Exact name of registrant as specified in its charter ) Delaware ( State or other jurisdiction of incorporation or organization ) 6100 Merriweather Drive , Columbia , Maryland , 21044 ( Address of principal executive offices , including zip code ) ( 410 ) 872-0555 ( Registrant's telephone number , including area code ) Title of each class Common stock , par value $ 0.01 per share 47-5580846 ( I.R.S. Employer Identification Number ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading symbol ( s ) Large accelerated filer Non - accelerated filer Name of exchange on which registered Nasdaq Global Select Market TENB 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 . Accelerated filer 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 . o 0 0 Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes No As of June 30 , 2020 , the aggregate market value of the common stock of the registrant held by non - affiliates was approximately $ 2.1 billion . The number of shares of the Registrant's common stock outstanding as of February 16 , 2021 was 104,036,276 . □ 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 . DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant's definitive Proxy Statement relating to the 2021 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10 - K . The Proxy Statement will be filed with the Securities and Exchange Commission within 120 days after the year ended December 31 , 2020 .