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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 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 fiscal year ended June 30 , 2021 OR CARDIOVASCULAR SYSTEMS , INC . ( Exact name of registrant as specified in its charter ) Commission file number : 000-52082 1225 Old Highway 8 Northwest St. Paul , Minnesota ( Address of principal executive offices ) Title of each class Common Stock , One - tenth of One Cent ( $ 0.001 ) Par Value Per Share 41-1698056 ( I.R.S. Employer Identification No. ) 55112-6416 ( Zip Code ) Registrant's telephone number , including area code : ( 651 ) 259-1600 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol CSII Large accelerated filer Emerging growth company Name of each exchange on which registered The Nasdaq Stock Market LLC 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 Exchange 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 Non - accelerated filer Smaller reporting 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 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 ✔ As of December 31 , 2020 , the aggregate market value of the registrant's common stock held by non - affiliates of the registrant was approximately $ 1,702.0 million based on the closing sale price as reported on The Nasdaq Stock Market LLC .