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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 December 31 , 2020 □ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( D ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Cayman Islands ( State or other jurisdiction of incorporation or organization ) 200 Clarendon Street , 55th Floor Boston , MA ( Address of principal executive offices ) ARCLIGHT CLEAN TRANSITION CORP . ( Exact name of registrant as specified in its charter ) 001-39546 ( Commission File Number ) Title of Each Class : Units , each consisting of one share of Class A ordinary share , 0.0001 par value , and one - half of one redeemable warrant 02116 ( Zip Code ) Registrant's telephone number , including area code : ( 617 ) 531-6300 Not Applicable ( Former name or former address , if changed since last report ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol : Class A ordinary shares included as part of the units Redeemable warrants included as part of the units ACTCU ACTC ACTCW Large accelerated filer Non - accelerated filer 98-1551379 ( I.R.S. Employer Identification Number ) ■ Name of Each Exchange on Which Registered : 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 | The Nasdaq Capital Market The Nasdaq Capital Market The Nasdaq Capital 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 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 and post 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 definition 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 . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes > No I X As of June 30 , 2020 , the last business day of the registrant's most recently completed second fiscal quarter , the registrant's securities were not publicly traded . The registrant's units began trading on The Nasdaq Capital Market ( " NASDAQ " ) on September 23 , 2020 and the gistrant's Class A shares , par value $ 0.0001 ( the " Class A ordinary shares " ) , and warrants began trading on NASDAQ on November 13 , 2020. The aggregate market value of the ordinary shares outstanding , other than shares held by persons who may be deemed affiliates of the registrant , computed by reference to the closing sales price for the ordinary shares on December 31 , 2020 , as