The rejection “BL Already on File” could mean two things. 

A. The manifest with the shipment was sent twice.

Resolution:

1. Contact CBP Help Desk to check if the SCN (current filing) exists on their record and verify the shipment and manifest details.
2. If the shipment is on file, then ask for support’s assistance to set the shipment status to Accepted (backend).

B. The shipment control number was already used.

Resolution:

1. Provide another shipment control number.
2. Change the existing SCN.
3. Save the shipment.
4. Save the manifest.
5. Resubmit as ADD.

NOTE: Make sure to inform the Broker of the new SCN.