This transaction set enables importers and customs brokers to request U.S. Customs and Border Protection (CBP) approval to transfer merchandise between ports of entry or bonded warehouses. The party filing the request—typically an importer, customs broker, or freight forwarder—sends the 356 to CBP to obtain authorization for the proposed transfer. The transaction set is structured around the M10 (Manifest Identifying Information) segment, which establishes the context for the transfer request, and the P4 (U.S. Port Information) segment, which identifies the source and destination ports involved. Multiple M20 (Permit to Transfer Request Details) segments within each port loop capture the specifics of each transfer request, including the merchandise, quantities, and conditions.

For example, Apex Import Solutions, a customs brokerage firm, submits a 356 transaction to CBP on behalf of its client, TechWare Inc., to transfer 500 units of electronic components from the Port of Los Angeles to the Port of New York for storage in a bonded warehouse pending further distribution. The ST header identifies the transaction type, the M10 segment references the specific shipment manifest number and arrival information, the P4 segment specifies Los Angeles as the port of unlading and New York as the destination, and the M20 segments detail the product classifications, quantities, and bond information for the merchandise transfer. CBP reviews the request and responds with approval or requests additional information before authorizing the transfer.