This document is designed to facilitate the understanding of the electronic format for transmitting Vehicles and Engines (V&E) regulated import data to Customs and Border Protection (CBP). Currently this data is submitted to Environmental Protection Agency (EPA) via two paper forms, 3520-1 and 3520-21. This guide addresses Form 3520-21. With the development of the Automated Commercial Environment (ACE), EPA can receive V&E data from Trade via ACE. Trade can electronically submit EPA data to CBP via the Partner Government Agency (PGA) Message Set. This document maps each data element from the V&E Form 3520-21 (Exhibit 1-1 and Exhibit 1-2) to its corresponding location within the EPA V&E PGA Message Set (Exhibit 1-3). This document is supplemental, and should be used in conjunction with EPA’s Supplemental PGA Message Set Documentation in order to create appropriate and complete submissions.