This transaction set communicates customs events and advisory details related to shipments entering the United States. U.S. Customs brokers, port authorities, and trade compliance service providers send the 353 to importers, logistics providers, and freight forwarders to provide notification of customs-related events affecting manifested shipments. The transmission typically occurs in response to customs activities or status changes at U.S. ports of entry. The M10 segment identifies the specific manifest, the P4 segment specifies the U.S. port location where the event occurred, and the M15 segment (repeating up to 9999 times) contains the detailed customs event information, allowing multiple events or advisory items to be communicated within a single transmission.

Consider a scenario where ABC Customs Brokerage receives a shipment manifest for TechCorp Industries arriving at the Port of Los Angeles. When U.S. Customs flags the shipment for inspection due to a trade compliance hold, ABC Customs Brokerage sends a 353 transaction to TechCorp detailing the event. The M10 segment references the manifest number, the P4 segment identifies Los Angeles as the port, and the M15 segment repeats twice—once to advise of the inspection flag and once to provide the specific compliance issue requiring documentation. TechCorp’s import compliance team receives the 353 and immediately understands the delay and the corrective action needed.