Why it is worth insisting on
A commercial invoice says what you bought. A packing list says what was put in the boxes. When those two disagree, the packing list is what the argument is settled on — and a short shipment discovered at your warehouse is very hard to prove without one.
It is also what a freight forwarder and a customs broker work from. A vague packing list delays clearance more reliably than almost any other missing document.
What a usable one contains
- Carton-by-carton contents, not a single line for the whole shipment.
- Net and gross weight per carton and in total. The gap between them is the packaging, and a large discrepancy against the bill of lading is worth asking about.
- Dimensions, so the volume can be checked against what you are being charged for.
- Marks and numbers matching the cartons themselves, so a specific box can be found.
Where it fits in a milestone
A packing list on its own proves very little — it is written by the supplier. It becomes evidence when it agrees with something produced by somebody else: an inspection report counting the same cartons, or a bill of lading issued by the carrier for the same weight.
Requiring all three is not belt and braces. It is the difference between a document and a corroborated document.