If you encounter an “invalid status of request/cargo control number” or “ccn in history” response when submitting an Add request, it means that the cargo control number has already been used and a new one must be assigned. To determine where the previous use of the cargo control number occurred, you can contact the carrier. Another option is to perform a status query through the Release Notification System (RNS), which can provide the information. For more details on the status query function, refer to the RNS Electronic Commerce Clients Requirements Document (ECCRD). If necessary, you can request a copy of the RNS ECCRD by emailing ECU.UCE@CBSA-ASFC.GC.CA.