As filed with the Securities and Exchange Commission on June 28, 2021. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 PROTERRA INC (Exact Name of Registrant as Specified in Its Charter) Delaware 3711 98-1551379 (State or Other Jurisdiction of (Primary Standard Industrial (I.R.S. Employer Incorporation or Organization) Classification Code Number) Identification Number) 1815 Rollins Road Burlingame, California 94010 Tel.: (864) 438-0000 (Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices) John J. Allen Chief Executive Officer 1815 Rollins Road Burlingame, California 94010 Tel.: (864) 438-0000 (Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service) Copies to: Dawn H. Belt JoAnn C. Covington Per B. Chilstrom Chief Legal Officer Fenwick & West LLP Proterra Inc 801 California Street 1815 Rollins Road Mountain View, California 94041 Burlingame, California 94010 (650) 988-8500 Tel.: (864) 438-0000 Approximate date of commencement of proposed sale to the public: From time to time after the effective date of this registration statement. If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. ⌧ If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐ If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐ If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐ 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. Large accelerated filer ☐ Accelerated filer ☐ Non-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 7(a)(2)(B) of the Securities Act. ☐ CALCULATION OF REGISTRATION FEE Proposed Maximum Proposed Maximum Title of Each Class of Securities to be Registered Amount to be Registered(1) Offering Price Per Share Aggregate Offering Price(1) Amount of Registration Fee Common stock, par value $0.0001 per share (2)(3) 168,719,124 $16.41 (7) $2,768,680,825 (7) $302,064(10) Warrants to purchase common stock(2)(4) 7,550,000 $— (8) $— (8) $— (8) Common stock, par value $0.0001 per share(2)(5) 21,424,994 $11.50 (9) $246,387,431 (9) $26,880.87(10) Common stock, par value $0.0001 per share(2)(6) 28,941,556 $0.02- $4.98 (9) $322,971 (9) $35.24 Total $241,456.86(10)(11) (1) Prior to the consummation of the Business Combination described in the prospectus forming part of this registration statement (the “prospectus”), ArcLight Clean Transition Corp., a Cayman Islands exempted company (“ArcLight” and, after giving effect to the Domestication (as defined below), “New Proterra”), effected a deregistration and a transfer by way of continuation to Delaware pursuant to Part XII of the Companies Law (as amended) of the Cayman Islands and Section 388 of the Delaware General Corporation Law, pursuant to which ArcLight’s jurisdiction of incorporation was changed from the Cayman Islands to the State of Delaware (the “Domestication”) as further described in the prospectus. Following the Domestication, New Proterra was renamed “Proterra Inc”. All securities being registered were or will be issued by New Proterra. (2) Pursuant to Rule 416(a) of the Securities Act of 1933, as amended (the “Securities Act”), there are also being registered an indeterminable number of additional securities as may be issued to prevent dilution resulting from stock splits, stock dividends or similar transactions. (3) The number of shares of common stock of New Proterra (the “common stock”) being registered for resale represents the sum of (i) 41,500,000 shares of common stock issued in a private placement described in more detail in the prospectus; (ii) 6,797,072 shares of common stock issued in connection with the consummation of the Business Combination, in exchange for Class B ordinary shares originally issued in a private placement to ArcLight CTC Holdings, L.P. (the “Sponsor”); (iii) 112,872,052 shares of common stock issued or issuable to certain former stockholders and other security holders of Proterra (the “Proterra Holders”) in connection with or as a result of the consummation of the Business Combination, consisting of (a) 59,946,701 shares of common stock (the “Proterra Holder Shares”); (b) 25,437,033 shares of common stock issuable upon the conversion of certain convertible notes (the “Note Shares”); (c) 3,421,902 shares of common stock issuable upon the exercise of certain warrants (the “Proterra warrants”); (d) 11,171,287 shares of common stock issuable upon the exercise of equity awards held by certain Proterra Holders; and (e) 12,895,129 shares of common stock that certain Proterra Holders have the contingent right to receive upon the achievement of certain stock price-based vesting conditions (the “Earnout Shares”); and (iv) 7,550,000 shares of common stock issuable upon the exercise of the private placement warrants (as defined below). (4) The number of warrants being registered represents 7,550,000 warrants (the “private placement warrants”) issued in connection with the consummation of the Business Combination, in exchange for warrants originally issued in a private placement to the Sponsor. (5) Represents 21,424,994 shares of common stock that may be issued upon the exercise of (i) 13,874,994 warrants to purchase common stock (the “public warrants”) and (ii) the private placement warrants. (6) Represents (a) 3,504,523 shares of common stock that may be issued upon the exercise of the Proterra warrants and (b) 25,437,033 Note Shares that may be issued upon the conversion of the convertible notes. (7) Estimated solely for the purpose of calculating the registration fee, based on the average of the high and low prices of the common stock on the Nasdaq Global Select Market on June 21, 2021 ($16.41 per share). This calculation is in accordance with Rule 457(c) of the Securities Act. See footnote 9 below for additional details. (8) No separate fee due in accordance with Rule 457(g). (9) Calculated pursuant to Rule 457(g) under the Securities Act, based on the applicable exercise prices of the various warrants. No additional consideration will be received by the registrant upon conversion of the convertible notes. (10) Calculated by multiplying the proposed maximum aggregate offering price of securities to be registered by 0.0001091. (11) Pursuant to Rule 457(p) under the Securities Act, the registrant is offsetting the registration fee due under this registration statement by $87,523.25, which represents the portion of the registration fee paid with respect to securities that had previously been included in the registrant’s registration statement on Form S-4 (Registration Statement No. 333-252674), which was originally filed with the Securities and Exchange Commission on February 3, 2021. The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine. The information in this preliminary prospectus is not complete and may be changed. The securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted. SUBJECT TO COMPLETION, DATED JUNE 28, 2021 PRELIMINARY PROSPECTUS Proterra Inc 168,719,124 Shares of Common Stock 7,550,000 Warrants to Purchase Shares of Common Stock 50,366,550 Shares of Common Stock Underlying Warrants and Convertible Notes ____________________ This prospectus relates to the offer and sale from time to time by the selling securityholders named in this prospectus (the “Selling Securityholders”) of (A) up to 168,719,124 shares of common stock, par value $0.0001 per share (“common stock”), consisting of (i) up to 41,500,000 shares of common stock (the “PIPE shares”) issued in a private placement pursuant to subscription agreements entered into on January 11, 2021 (the “PIPE Financing”); (ii) up to 6,797,072 shares of common stock (the “founder shares”) issued in connection with the consummation of the Business Combination (as defined below), in exchange for shares of our Class B ordinary shares originally issued in a private placement to ArcLight CTC Holdings, L.P.