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UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C. 20549 FORM 10 - Q ( Mark One ) ☑ ☐ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31 , 2021 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Delaware Commission File Number 001-38267 RIBBON COMMUNICATIONS INC . ( State or other jurisdiction of incorporation or organization ) ( Exact name of Registrant as specified in its charter ) 82-1669692 ( I.R.S. Employer Identification No. ) 6500 Chase Oaks Boulevard , Suite 100 , Plano , Texas , 75023 ( Address of principal executive offices ) ( Zip code ) ( 978 ) 614-8100 ( Registrant's telephone number , including area code ) N / A ( Former name , former address and former fiscal year , if changed since last report ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common Stock , par value $ 0.0001 Trading Symbol ( s ) RBBN Name of each exchange on which registered The Nasdaq Global Select Market 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 x No o 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 x Noo 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 Smaller reporting company ☐ ☐ Accelerated filer Emerging growth company П Non - accelerated filer ☐ 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 Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes □ No x As of April 23 , 2021 , there were 147,367,469 shares of the registrant's common stock , $ 0.0001 par value per share , outstanding .