This transaction set enables the electronic submission of in-bond shipment information to U.S. Customs authorities. Typically sent by freight forwarders, customs brokers, or importing companies to the U.S. Customs and Border Protection (CBP) agency, the 357 is usually transmitted to report goods moving under customs bond through U.S. ports. The transaction’s backbone consists of the M10 segment (Manifest Identifying Information), which establishes the manifest details; the P4 segment (U.S. Port Information), which specifies the port of entry or departure; and the M12 segment (In-bond Identifying Information), which documents the specific bond details and shipment routing for each commodity or container included in the filing.

For example, Global Freight Solutions, a customs broker based in Long Beach, California, receives a shipment of electronics from a supplier destined for assembly in Mexico under temporary importation bond. Global Freight Solutions prepares and transmits an X12 357 transaction to CBP containing one manifest (M10) identifying the shipment, the port information (P4) for Long Beach, and multiple in-bond records (M21/M12 pairs) detailing each palletized lot, its bond type, and its intended export destination. CBP receives this structured data, validates the bond compliance, and grants entry authorization, allowing the containers to proceed through the port without immediate duty payment or formal entry processing.