The port of discharge and port of discharge sub-loc code are conditional fields, and the condition is “when available”. If the port of discharge sub-loc code is available, it must be presented, and the port of discharge code must also be presented. If the port of discharge sub-loc code is not available, it does not need to be provided, and the port of discharge code should not be provided. If the port of discharge code is provided, the port of discharge sub-loc code must also be provided.