Guides / Compliance

How AQL Inspection Works, and Which Level to Put in Your Contract

September 9, 2026

AQL, acceptable quality level, is the rule that decides whether a finished batch is accepted or rejected. It shows up on every inspection report, and it is quoted confidently by people who have misread what it promises.

This guide covers what the numbers mean, how the sample size is chosen, where in production to inspect, and what to write into your purchase order so a failed lot has a defined consequence.

What AQL is, and what it is not

An inspection does not check every unit. It draws a sample, counts defects in the sample, and compares the count against an accept number. AQL is the input that sets that accept number.

So AQL 2.5 does not mean you accept 2.5 percent defective goods. It means the sampling plan is built so that lots at or better than that quality level are usually accepted and worse lots are usually rejected. It is a filter with known behaviour, not a guarantee.

Two consequences follow. A passing lot can still contain defects, so a passing report is not a promise of perfection. And a single rejected lot is not proof of disaster, it is a signal to look harder.

Sample size comes from lot size, not from opinion

Standard sampling tables take your lot size and an inspection level, and return a sample size code. That code plus your AQL gives the number of units to draw and the maximum defects allowed.

The practical points for a buyer:

• Sample size grows much more slowly than lot size. Doubling your order does not double the inspection cost.
• General inspection level II is the normal default for finished goods.
• Tightening the AQL raises the sample size and therefore the inspection time.
• The sample must be drawn across the lot, not from whatever is nearest the door. An inspector who accepts a pre-stacked sample is not inspecting.

Defect classes do most of the work

The classification is where buyers gain or lose, and it is usually left vague.

Critical. Makes the product unsafe or illegal to sell. The standard practice is zero tolerance.

Major. Affects function, fit or durability, or would cause a return. Commonly run at 2.5.

Minor. Cosmetic or trivial, unlikely to be noticed or to cause a return. Commonly run at 4.0.

The argument on site is almost never about the numbers. It is about whether a given scratch is major or minor. Which is why the single most valuable document in an inspection is not the AQL table, it is the defect classification list you wrote and the approved sample it refers to.

Write a short list, with photographs, of what counts as each class on your specific product. Ten lines is enough and it removes most of the disputes.

Where to inspect

Three points, each answering a different question.

During production, at around 20 percent complete. Answers whether the line is set up correctly while there is still time to fix it. This is the highest value inspection and the one most often skipped.

Pre-shipment, at 100 percent produced and at least 80 percent packed. Answers whether the finished lot is acceptable. This is the one that gates your final payment.

Container loading. Answers whether what passed actually went into the box, loaded correctly. Worth it on fragile goods and on products where mixed SKUs are easy to load wrong.

On a first order with a new factory, the during-production check earns its cost more reliably than anything else you can buy.

Write it into the order

Four lines in the purchase order, agreed before production:

1. The inspection standard, level and AQL by defect class.
2. The approved sample the inspection is measured against, and where it is held.
3. Who inspects and who books them.
4. The consequence of a fail: who pays for sorting, rework and re-inspection, and whether final payment is held until a pass.

Without the fourth line the first three are decoration. A factory that has already agreed in writing that it pays for rework behaves differently from one discovering the idea after a failed lot.

The golden sample is the reference

Every inspection compares goods to a reference. If the reference is an email thread, the inspection is an argument. If it is a physical approved sample, signed and held by both sides, the inspection is a measurement.

That sample comes out of the pilot run. See the pilot run and the golden sample for how to set it up so the reference is real.

Inspection is not a substitute for capability

Inspecting your way to quality is expensive and it fails slowly. If a factory needs heavy inspection to ship acceptable goods, the problem is upstream: process control, incoming material, or a specification the factory never had a realistic chance of holding.

That is what the factory audit is for, and the two tools work together. How a factory audit in Vietnam works covers the other half.

Booking the inspection

Three practical points that decide whether an inspection happens usefully or at all.

Book early and confirm readiness. Inspection bodies schedule days in advance, and the single most common failure is an inspector arriving to find the lot is not finished or not packed. Ask the factory to confirm the completion percentage the day before.

Say who is allowed to release the goods. If the factory can ship a rejected lot because the forwarder was already booked, the inspection was decorative. The release authority should sit with you.

Require the report before the balance payment. Not the summary by email, the report with photographs and the measurement sheets.

Reading the report properly

Inspection reports look intimidating and the useful parts are consistent.

Check the sample size against the lot size first. If the lot grew after you agreed the plan, the sample should have grown with it. Then read the defect list rather than the verdict, because a lot can pass while telling you something important. Twelve minor cosmetic defects of the same type in one sample is a process drifting, even if the plan accepts it.

Look at the photographs of the packing and the carton markings. Inspectors routinely catch wrong labels, missing origin marking and barcodes that will not scan, and those are the defects that cause problems at customs or at a retailer’s receiving dock rather than with the customer.

Finally, check what was not inspected. Reports state their scope. A pre-shipment inspection that covered appearance and packing but not function is a partial answer, and on a functional product you want the functional tests named.

Who should inspect

Three options, with different economics.

The factory’s own quality team. Free, and it is not an independent check. Useful for in-process control, not useful as the gate on your final payment.

A third party inspection body. The normal choice. Priced per man-day, booked a few days ahead, and independent of the factory. On a first order this is the one to use.

Your own person on site. Best information, highest cost, and only realistic when you have someone in the country or the order justifies travel.

A common and sensible pattern is a third party during production and before shipment on the first two orders, then stepping back to pre-shipment only once the factory has shown it holds the standard.

Whoever inspects, give them the approved sample, the defect classification and the drawing. An inspector without a reference is producing an opinion in a report template.

Send your brief with the inspection standard you intend to use, and we will match you with manufacturers that are used to working to it.

Frequently asked questions

Keep reading

• Food Contact Materials Compliance for Goods Made in Vietnam
• During Production Inspection: The Check That Saves the Order