Trailer number
Use the equipment identifier provided for the load. It helps the shipper, driver, carrier, and receiver connect the printed BOL to the equipment at pickup or delivery.
Shipment identification
Trailer and seal numbers on a bill of lading: a simple handoff record
Record a trailer number or seal number when the carrier, customer, or security process calls for it. The value is a clear handoff record: the number on the document should match the equipment or seal actually used for this shipment.
Use the number that exists at the handoff—not a placeholder
A trailer number identifies the equipment carrying the shipment. A seal number identifies the particular seal applied to a trailer or container. They are operational references, not substitutes for a BOL number, carrier PRO number, or shipment barcode.
Both fields are often unknown when a shipper first prepares paperwork. Leave a field blank until the correct number is assigned, or follow the carrier’s approved correction process. A guessed number makes reconciliation harder than an intentionally blank field.
A seal number is only one part of a security process
Do not treat the BOL entry as proof that a seal was applied, intact, or accepted. Follow the carrier, customer, and site process for applying, recording, verifying, and responding to a seal exception.
Keep equipment and seal references in the right lane
Seal number
Record the unique number printed on the seal when a seal is actually applied and the process requires it. Check every character against the physical seal before the trailer leaves.
BOL and PRO number
Keep shipment and carrier tracking IDs in their own fields. A trailer can carry several shipments over time, and a BOL may not have a trailer number when initially prepared.
Exception handling
If equipment or seal information changes, follow the carrier or customer process for recording the change. Do not quietly overwrite an earlier record without a traceable handoff.
Before the equipment leaves
- 1Confirm whether the customer, carrier, or security plan requires a trailer number, seal number, or both.
- 2Compare the written trailer number to the equipment at pickup.
- 3If a seal is applied, compare the BOL entry to the number physically printed on the seal.
- 4Record the number only after the final equipment or seal is known.
- 5Follow the documented escalation process for a mismatch, broken seal, or equipment change.
Trailer and seal questions
Do I need a trailer number on every BOL?
No universal rule makes it necessary for every domestic shipment. Add it when the carrier, customer, pickup site, or shipment process needs the equipment reference.
Can I put a seal number on the BOL before sealing the trailer?
Wait until the actual seal is known, unless the approved process has assigned a specific seal in advance and requires that record. The final document should match the physical handoff.
Is a seal number the same as a PRO number?
No. A seal number identifies a particular physical seal. A PRO number is a carrier-issued shipment-control or tracking reference. Both may appear on the same BOL but answer different questions.
Related guides
Sources & scope
Updated August 22, 2026. Scope: U.S. domestic general freight. Seal, trailer, and security procedures are carrier-, facility-, customer-, and commodity-specific. Follow the approved operational and security process for the shipment.
- Maersk: Container seal numbers — seal-number recording and delivery verification context
- FMCSA supporting-document guidance — BOLs as normal-course business records showing trip origin and destination
Keep the final handoff number on the BOL
DockBOL includes separate trailer and seal fields beside the carrier information, so the equipment reference stays visible without being confused with the BOL or PRO number.
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