This document proposes amendments to the U.S Customs and Border Protection (CBP) regulations relating to the importation into the United States of certain vehicles and engines subject to federal antipollution emission standards under the Clean Air Act (CAA). Compliance with these emission standards must be demonstrated to CBP by either filing, or retaining and producing upon request, the appropriate U.S. Environmental Protection Agency (EPA) declaration form or by establishing that the subject imports are exempt from this requirement. CBP is proposing to amend its regulations to harmonize the documentation requirements applicable to different classes of vehicles and engines that are subject to the CAA’s emission standards. This document also proposes to permit the required EPA emission compliance forms to be filed with CBP electronically. CBP is proposing other non-substantive amendments to update regulatory citations and delete obsolete provisions. The proposed changes set forth in this document support consistency in the administration of CBP’s vehicle and engine imports program. In addition, electronic filing of EPA declaration forms will support key modernization initiatives, expedite the entry and clearance process, enhance targeting and enforcement objectives, and connect CBP with partner government agencies and the trade community through a single window access point.