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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 January 31 , 2021 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 Delaware ( State or other jurisdiction of incorporation or organization ) For the transition period from to Commission file number : 001-38926 Slack Technologies , Inc. ( Exact name of registrant as specified in its charter ) 500 Howard Street San Francisco , California 94105 ( Address of principle executive offices including zip code ) ( 415 ) 630-7943 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) Name of each exchange on which registered The New York Stock Exchange Title of each class Class A Common Stock , $ 0.0001 par value per share WORK 26-4400325 ( 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 or 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 or > 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 or □ 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 or No. Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , 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 Accelerated filer Smaller reporting company Emerging growth company 000 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 . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes or > No The aggregate market value of the registrant's Class A common stock , $ 0.0001 par value , held by non - affiliates of the registrant ( based on $ 29.55 , which was the closing price of a share of the registrant's Class A common stock on July 31 , 2020 , as reported by the New York Stock Exchange ) was approximately $ 14.1 billion . Shares of common stock held by each executive officer , director and holder of 5 % or more of the outstanding common stock have been excluded in that such persons may be deemed to be affiliates . This determination of affiliate status does not reflect a determination that such persons are affiliates of the registrant for any other purpose . There were 502,550,914 shares of the registrant's Class A common stock outstanding and 79,095,890 shares of the registrant's Class B common stock outstanding as of February 28 , 2021 .