What pre-shipment inspection is
Pre-shipment inspection is a check of finished goods, made at the factory before they leave, in which an inspector draws a statistical sample from the lot and examines it against the buyer's specification. For goods made in China it is usually the last point at which a buyer can find a defect while the goods, the factory and the unpaid balance are all still in one place.
Pre-shipment inspection (PSI) is one stage of a broader practice usually called quality inspection or quality control (QC). The terms for the stages are industry conventions, not categories defined by any regulator. The buyer, or an agent acting for it, commissions the work, either from a third-party inspection company or from its own in-house QC staff. The inspector reports what was found; the buyer decides whether to accept the lot, ask for rework or refuse shipment.
An inspection is evidence about a sample on a given day. It is not a certificate that every unit conforms, and it is not a substitute for regulatory testing. Both limits are discussed below, because they are where importers most often overestimate what a passed report means.
The four inspection stages
Inspections are timed to catch different kinds of failure. The common stages are:
| Stage | When | What it catches |
|---|---|---|
| Pre-production inspection (PPI, also IPC) | Before mass production | Wrong raw materials or components; problems in the first production units |
| During-production inspection (DUPRO, also DPI) | Typically when a portion of the order is complete | Systemic defects while correction is still possible |
| Pre-shipment inspection (PSI, also final random inspection) | Goods finished and mostly packed | Workmanship, function, labeling and packing defects across the lot, using AQL sampling |
| Container loading supervision (CLS) | At loading | Short quantities, packing and carton condition, container condition; often records the seal |
The stages are cumulative rather than alternatives. A PSI that finds a systemic defect in a finished, packed order leaves the buyer choosing between delay, rework and acceptance at a discount. A DUPRO that finds the same defect earlier costs far less to correct. New products, new factories and orders with custom tooling are where earlier stages earn their place.
How AQL sampling works
AQL (acceptance quality limit) is the worst tolerable process average of defects for a sampling plan — the defect level the buyer is prepared to accept as a long-run average. It comes from the sampling schemes of ISO 2859-1, published by the International Organization for Standardization (ISO) as the international standard for sampling by attributes, and its US counterpart ANSI/ASQ Z1.4, which derives from the military standard MIL-STD-105E.
The mechanics, as defined in the ISO 2859-1:1999 and Z1.4 framework, run in a fixed sequence:
- Choose an inspection level. General levels I, II and III, or special levels S-1 to S-4 for tests where only small samples are practical.
- Choose an AQL for each defect class. Defects are graded critical (unsafe or illegal), major (likely to cause failure or a return) and minor (a departure from specification that does not affect use), and each class gets its own AQL.
- Read the sample-size code letter. Lot size and inspection level together give a code letter.
- Read the plan. The code letter and the AQL give a sample size, an acceptance number (Ac) and a rejection number (Re).
- Count and decide. If the defects found are at or below Ac, the lot is accepted; at or above Re, it is rejected.
The point to keep in view is that AQL sampling controls the buyer's risk statistically. A lot accepted at an AQL is not a lot with no defects; it is a lot whose sample did not exceed the acceptance number. This is also why "AQL 2.5" on its own is an incomplete instruction. Without the inspection level and the defect class, it does not define a sampling plan.
Which AQL standard applies in 2026
The edition matters, because inspection contracts and reports often cite it by year. As of 30 October 2026, the ISO catalog entry for ISO 2859-1:1999 (Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection, edition 2, published November 1999) shows it as withdrawn (stage 95.99) and "revised by ISO 2859-1:2026." Its 2011 amendment and 2001 corrigendum are also listed as withdrawn.
What changed in the 2026 edition — whether its tables, code letters or switching rules differ from the 1999 text — has not been confirmed for this guide, and its exact publication date has not been verified. The current designation and reaffirmation year of ANSI/ASQ Z1.4 were also not verified. The practical consequence is narrow but real: an inspection specification or supplier contract that names "ISO 2859-1:1999" as the governing standard now names a withdrawn document. Buyers should confirm which edition their inspector applies and update their own documents to reference the current edition once its contents are checked.
Writing the inspection checklist
An inspector can only test against what the buyer has written down. The checklist should be drafted from two documents: the approved golden sample (the signed and sealed reference sample retained by buyer and factory) and the written product specification referenced in the supply contract. A checklist built from memory or from the factory's own documents tests the factory's idea of the product, not the buyer's.
A usable checklist typically covers:
- Defect definitions by class — what counts as critical, major and minor for this product.
- Measurements and tolerances — dimensions, weights and the method of measuring them.
- Function and on-site tests — what the inspector should operate, fit or drop-test.
- Labeling and marking — including country-of-origin marking and any required product labels.
- Packing — carton marks, inner packing, quantity per carton and carton condition.
- The sampling plan — inspection level and AQL for each defect class, and the edition of the standard.
Two procedural points decide whether the result can be trusted. The inspector, not the factory, should choose the sample cartons. And the inspection should be scheduled before the balance payment falls due, so that a failed report still has commercial consequences.
What inspection does not prove
A passed pre-shipment inspection shows that a sample met the workmanship and specification criteria on the checklist. It does not show compliance with safety and product regulations. Regulated testing — for example under CPSC rules for consumer products, FCC rules for electronic devices, or REACH requirements in the European Union — is a separate activity, normally performed by a testing laboratory to a defined method. Treating an inspection report as a compliance document is one of the most common and most expensive misreadings in China sourcing.
Border enforcement illustrates the gap. In its FY2025 intellectual property rights seizure statistics, US Customs and Border Protection reported seizures including 1,187,193 consumer-electronics items and 880,546 toys by quantity, and found that 62% of IPR seizures occurred in containerized commercial-vessel cargo. CBP attributes that shift away from small parcels to the suspension of de minimis treatment for China and Hong Kong shipments in May 2025 and for all countries in August 2025. Two cautions apply: these figures measure intellectual property violations, not quality defects, and CBP states the publication is not official trade statistics. What they do show is that containerized B2B imports are now squarely within enforcement, and a factory inspection checklist does not test for the problems customs looks for.
Who performs inspections and how cost is structured
Inspection is performed either by a third-party inspection company engaged by the buyer or by the buyer's own QC staff. Where a sourcing agent arranges inspection, the buyer should know whether the inspector is independent of the party that selected the factory; an agent inspecting its own choice of supplier has a conflict of interest. This guide does not rate or name inspection companies.
In most markets inspection is quoted per person-day, with travel added. The main cost drivers are structural: the number of person-days a sample size requires, the number of stages ordered, the factory's location, and whether on-site tests need special equipment. Price levels change and are not given here.
No official statistic on inspection failure rates for Chinese factories was found. Inspection companies publish their own figures, but they are not neutral sources and should be read as marketing data.
Common mistakes
- Citing "AQL 2.5" without an inspection level or defect class. The plan is undefined.
- Treating a passed PSI as proof of regulatory compliance. Lab testing is separate.
- Letting the factory choose the sample cartons. The sample stops being random.
- Paying the balance before the inspection report arrives. A failed report then has no commercial weight.
- Specifying the withdrawn 1999 edition without checking the 2026 revision.
- Inspecting only at the end on a first order from a new factory, when an earlier stage would have caught a systemic defect.
Frequently asked questions
What is AQL in quality inspection?
AQL, the acceptance quality limit, is the worst tolerable process average of defects in a sampling plan under ISO 2859-1 or ANSI/ASQ Z1.4. With the lot size and inspection level, it sets the sample size and the acceptance and rejection numbers. It controls risk statistically: an accepted lot can still contain defective units.
Is ISO 2859-1:1999 still current?
No. As of 30 October 2026, the ISO catalog lists ISO 2859-1:1999 as withdrawn and revised by ISO 2859-1:2026, with its 2011 amendment and 2001 corrigendum also withdrawn. The contents of the 2026 edition were not verified for this guide, so check whether its tables differ before updating an inspection specification.
When should a pre-shipment inspection happen?
A pre-shipment inspection normally takes place when production is complete and most of the goods are packed, so the sample represents the finished lot. That is industry practice rather than a regulatory rule. It should also fall before the balance payment is due, so that a failed result can still delay shipment or payment.
What is the difference between DUPRO and PSI?
A DUPRO, or during-production inspection, takes place while the order is being made, typically once part of it is complete, and aims to catch systemic defects while they can still be corrected. A PSI, or pre-shipment inspection, examines the finished and mostly packed lot using AQL sampling to decide whether to accept it.
Does a quality inspection replace lab testing?
No. An inspection checks workmanship and conformity to the buyer's specification on a sample. Regulated safety testing, such as testing under CPSC, FCC or REACH requirements, is a separate activity normally carried out by a laboratory to a defined method. A passed inspection report is not evidence of regulatory compliance.
What does AQL 2.5 mean?
AQL 2.5 means the sampling plan is indexed to an acceptance quality limit of 2.5 for a given defect class, but the figure alone is incomplete. The sample size and acceptance number also depend on the lot size and the inspection level chosen, and buyers usually set different AQLs for critical, major and minor defects.