A pre-shipment inspection is a sampling exercise carried out when 80% or more of an order is packed. The inspector pulls a sample sized by the AQL standard (for a 10,000-piece order at AQL 2.5, that is typically 200 units) and checks workmanship, measurements against the specification, function on a subset, and packaging and labelling. It does not verify the quantity of the whole shipment, does not test durability or long-term reliability, and does not confirm that what is loaded into the container is what was inspected. A passed inspection is evidence the sample conformed on the day, which is why it is worth tying a payment tranche to, and why it is not a guarantee of the shipment.
Buyers who have never commissioned one tend to imagine an inspection as a person checking the order. It is not that. It is a statistical sample, taken on one day, against a standard somebody agreed in advance, and knowing exactly where its edges are is what makes it useful as a payment condition rather than a comfort blanket.
When it happens
At 80% or more production completion, with the goods packed. Earlier and there is nothing representative to sample; later and the container is loaded, at which point finding a problem is expensive for everyone.
That 80% figure is worth holding on to when you set milestone dates. Book the inspector against a production date rather than a ship date, because the two diverge constantly and the inspection is the one that has to move first.
What the inspector does
Quantity of the presented lot. They confirm the cartons in front of them match the quantity declared for inspection. This is not the same as confirming your whole order exists. See below.
Workmanship, by sample. The sample size comes from the AQL standard, not from a guess. For a 10,000-piece order inspected at General Inspection Level II, the sample is typically 200 units. Defects are sorted into critical, major and minor, and each has its own acceptance number.
Measurements against your specification. Only the dimensions you specified. An inspector cannot check a tolerance nobody wrote down, and "matches the sample we approved" is not a dimension.
Function, on a subset. Usually a smaller sample than the visual check. If your product needs a specific test, such as a drop test, a load test or an hours-of-operation test, it must be named in the inspection brief.
Packaging, labelling and barcodes. Frequently where problems are found, and frequently the cheapest to fix while the goods are still in the factory.
What AQL numbers actually mean
AQL 2.5 does not mean "2.5% of your goods will be defective". It means the sampling plan is built to accept lots at that defect rate and reject worse ones, with a known probability of being wrong in either direction.
The practical consequence: a passed inspection at AQL 2.5 is consistent with a real defect rate above 2.5%. It is a filter, not a certificate. Common practice is 0 critical, AQL 2.5 major, AQL 4.0 minor. But the numbers are yours to set, and tightening them costs inspection time rather than money.
The three things buyers assume are covered
The quantity of the whole shipment. The inspector counts what is presented. A factory short-shipping by 5% will usually present a complete lot for inspection.
Durability. Nothing in a standard pre-shipment inspection tells you whether the product survives six months of use. That is a different test, commissioned separately, usually on pre-production samples.
That the inspected goods are the goods that ship. The inspection happens, the inspector leaves, and the container is loaded afterwards. Sealing the container in the inspector's presence, a loading supervision booked as a separate service, is what closes that gap, and it is worth doing on a first order with an unproven factory.
Why it still works as a payment gate
Because it is independent, it is dated, and it produces a document with a number in it. A tranche released against a passed report is released against something a third party wrote down, and both sides agreed the threshold before anybody had an interest in the answer.
Set it up so the inspector reports to you and is paid by you. An inspection the factory commissioned and forwarded is not the same evidence, whatever the letterhead says. If a factory objects to a buyer-appointed inspector on a first order, that is information.
Practical brief
Name these before the order, not after:
- The inspection standard and levels: critical, major, minor.
- Every dimension and tolerance that matters, in writing.
- Any functional test, with its pass criteria.
- Whether packaging, labelling and barcodes are in scope.
- Who books the inspector, and who pays.
- What happens on a fail: rework and re-inspect at whose cost, and who pays for the second visit.
People forget that last clause. It is what decides how a bad inspection resolves.