19 CFR § 143.31 - Applicability.
This subpart sets forth general requirements for the entry of imported merchandise processed electronically through the CBP Automated Commercial Environment (ACE) or any other CBP-authorized electronic data interchange system. Entries processed electronically are subject to the documentation, document retention and document retrievability requirements of this chapter as well as the general entry requirements of parts 141 and 142. Use of this system is voluntary and optional on behalf of the filer. Customs does not contemplate that processing of non-electronic filings shall be delayed.