ITN stands for internal transaction number. It is a number generated by the automated export system, and it is assigned to a shipment to confirm that the appropriate electronic export information is accepted and is on file in the AES, explains the U.S. Customs & Border Protection.
Export shipments are required to be filed electronically to the AES, which is a computerized system for processing electronic export information. The export information is entered into the AES system, and once accepted, an ITN is generated. The ITN serves as evidence of filing and compliance with applicable laws and regulations, and prior to exportation, it must be posted on loading documents, explains the U.S. Census Bureau.