“We will inspect before shipment” sounds like a plan until the goods are on the truck and nobody agreed which stage that meant, which defects would fail the lot, or how many pieces would actually be opened. An inspection clause with no numbers behind it is not a control; it is a sentence in an email that neither side can act on when something goes wrong.
Below is where inspection actually happens across an order’s life, how the sampling maths behind “AQL” works so a defect count means something, and what has to be written into the purchase order before the first unit is made.
💬 Setting up an inspection plan for an order already in progress? Tell us the product and the stage you are at and we will help you write it.
When in the order does inspection actually happen?
Four distinct points, each catching a different failure — and skipping to the last one means every earlier failure is now baked into a finished, packed shipment.
| Stage | When | What it catches | What it cannot catch |
|---|---|---|---|
| Pre-production check | Before mass production starts | Wrong material, wrong tooling, a sample that does not match the approved reference | Anything that happens during the production run itself |
| During-production check (DUPRO) | Partway through the run, commonly around 20–30% complete | A process drifting from what the sample approved — a finish, a dimension, a consistent assembly error | A problem that appears only near the end of the run, or after ageing |
| Pre-shipment inspection (PSI) | After the order is finished and packed, before it leaves the factory | Defect rate against the agreed AQL, packing, labelling, carton count and markings | Anything hidden inside a sealed unit that visual and functional checks do not open |
| Loading supervision | While the container is being loaded | Wrong quantity loaded, wrong cartons loaded, condition of the container itself, seal number recorded correctly | Nothing about the goods that pre-shipment inspection was meant to already confirm |
The names in the trade are not standardised word for word, but the four points above are the ones worth naming in a contract, because each is a different moment to catch a different class of problem. Pre-shipment inspection is the one buyers most often specify and the one most often reduced to “we checked it,” without saying what “checked” means — which is what the rest of this article fixes. Sunsho Trade coordinates inspection at any of these four points from Ho Chi Minh City, as part of our sourcing service.
What does “AQL” actually mean?
The Acceptable Quality Limit is the worst defect rate in a lot that a stated sampling plan will still accept most of the time — it is a sampling risk you choose, not a promise that the lot is defect-free.
ISO 2859-1 (identical in substance to the older MIL-STD-105E) sets out sampling plans for inspection by attributes — pass or fail per unit, not a measured value. Three things decide which plan applies to your order:
- Lot size — the number of units in the shipment or batch being inspected.
- Inspection level — General Inspection Level II is the default the standard itself specifies unless a reason exists to use Level I (less discrimination, smaller sample) or Level III (more discrimination, larger sample).
- The AQL value chosen for each defect class — a smaller number is a stricter limit.
From lot size and inspection level, the standard’s own tables give a sample size — the number of units actually opened and checked, always smaller than the full lot. From the sample size and the AQL value, the same tables give an acceptance number and a rejection number: found at or below the acceptance number of defects in that class, the lot passes; at or above the rejection number, it fails.
Which AQL value for which defect?
The standard does not set the values for you — you choose one AQL for each of three defect classes, and the classes are what make the sampling meaningful.
| Defect class | What it means | Commonly used AQL value | Example |
|---|---|---|---|
| Critical | Could cause injury, or breaches a safety or legal requirement | 0 — no critical defects are acceptable in the sample | A sharp edge on a children’s product, a missing required warning |
| Major | The unit will not work, or a buyer would very likely reject it | Commonly 1.0–2.5 | A zipper that does not close, a seam that fails under normal use |
| Minor | A defect a buyer might still accept, generally cosmetic | Commonly 2.5–4.0 | A small colour variation, a label placed slightly off-centre |
These figures are commonly used industry defaults, not fixed by the standard itself — the standard supplies the sampling maths once you have chosen the numbers, and different buyers legitimately set different values for the same product depending on how strict they need to be. Put the three values in the purchase order in writing; without them “AQL inspection” describes a method with no threshold, which settles nothing when a lot is on the line.
What goes into a defect list before the inspector arrives?
A written defect classification list, agreed before the inspection, is what turns “the inspector said it failed” into something both sides can check against the same document afterwards.
Build the list from the specification itself, sorted into the three classes above, and cover at minimum:
- Dimensional and functional defects specific to the product.
- Cosmetic and finish tolerances, stated concretely rather than as “acceptable quality” — a phrase with no meaning on a factory floor.
- Labelling and marking checks, including country-of-origin marking where the shipment needs it.
- Packing checks — carton condition, count per carton, and whether the export pack matches what was quoted (see comparing Vietnamese supplier quotations on the packing line that too often goes unspecified).
- A named reference — the approved pre-production sample, a limit sample, or dated photographs — that the inspector checks the goods against rather than a written description alone.
Where the goods are food, feed, plants or wood packaging, the pre-shipment inspection above is separate from any state health or quarantine certificate required to export the goods at all — see the export shipping documents checklist for where those fit in the paperwork.
💬 We can build the defect list against your specification and sit in on the inspection. Send us the product and the spec.
What to put in the purchase order
An inspection clause is enforceable only if it names the stage, the standard, the numbers and the consequence — a general clause promising “quality inspection before shipment” commits nobody to anything specific.
- Which of the four stages apply to this order, and at what point in the schedule each happens.
- The inspection standard: “ISO 2859-1, General Inspection Level II” plus the three AQL values, by defect class.
- The defect classification list, referenced or attached.
- Who performs the inspection — factory self-inspection, the buyer’s own staff, or a named third party — and who bears the cost.
- What happens on a failed lot: rework and re-inspect, partial acceptance, or full rejection, and who bears the cost of a re-inspection.
- The sample or reference the inspector checks against, and how it is stored so both sides can point to the same physical object later.
A clause with all of this in it is a document either side can hold the other to; a clause without it is a hope.
💬 If writing this into a purchase order for the first time feels like a lot to get right, that is exactly what our sourcing and quality coordination does day to day. Start with your next order.
Frequently asked questions
1. Is AQL 0 always the safest choice?
Only for the critical class, where it belongs. Applying AQL 0 across every defect class makes almost any lot fail on trivial cosmetic points, which does not make the product safer — it makes the inspection unusable and invites the factory to argue every finding.
2. Does passing a pre-shipment inspection mean the whole shipment is defect-free?
No. Sampling inspection accepts a stated risk that some defective units remain in an accepted lot; that is what “acceptable quality limit” means. It substantially reduces risk on a defined basis — it does not eliminate it, and a 100% inspection is a different, more expensive request if you need that guarantee.
3. Who should perform the inspection — the factory, the buyer, or a third party?
Any of the three can work, and the right choice depends on the order’s value and the trust built up with the factory; a self-inspection report from a factory you have shipped with several times is very different evidence from one on a first order. What matters more than who performs it is that the standard, sample size and AQL values are agreed before the inspection, not decided by whoever shows up.
4. What happens if we did not agree an AQL and now dispute a defect rate?
Without an agreed standard, sample size and AQL value in the purchase order, “too many defects” is a subjective claim each side can contest. This is why the clause needs the numbers before production starts, not after a dispute begins.
5. Does pre-shipment inspection replace the sample approval process?
No — they check different things. Sample approval confirms the product design and specification before mass production; pre-shipment inspection confirms the finished lot against that already-approved reference. See proto, fit and pre-production sample stages for where the two connect.
Sources: International Organization for Standardization, ISO 2859-1, Sampling procedures for inspection by attributes. Checked on 25 September 2026.