A verified supplier and a good sample do not guarantee that production will meet your specs. Most quality disputes don’t come from a supplier being dishonest — they come from a lack of inspection, or from inspections scheduled at the wrong time. Here’s how to structure quality control for an order from China, and what a serious inspection actually checks.
The three key moments to inspect — not just one
A single final inspection at the end of production is too late to fix anything — you’re just documenting the damage. Industry-standard practice uses three checkpoints:
- Before production: Verification of raw materials and components received by the factory, to confirm they match specifications before production starts.
- During Production Inspection (DPI): Carried out when 20 to 30% of the order is produced. It allows you to catch a systematic defect before it repeats across the entire batch.
- Pre-Shipment Inspection (PSI): The final check, once at least 80% of the order is packed. This is the only point where you see the product that is actually about to ship.
For a first order with a new supplier, all three are worth doing. For a repeat order with a proven supplier, a PSI alone is often sufficient.
The AQL standard: the foundation of any serious inspection
AQL (Acceptable Quality Limit, per ISO 2859-1) defines how many defective units are tolerated in a sample, based on the lot size. An inspector does not check 100% of the order — they take a statistically representative sample (General Inspection Level II is the most common standard) and classify any defects found into three categories:
- Critical: Makes the product dangerous or completely unusable — zero tolerance.
- Major: The product works but does not meet the specification or would likely be rejected by the end customer — common threshold AQL 2.5.
- Minor: A cosmetic defect that does not affect function — common threshold AQL 4.0.
Setting these thresholds in writing before the inspection takes place prevents disagreements afterward about what counts as a defect.
What a pre-shipment inspection actually covers
A serious PSI goes far beyond a quick visual check. It typically covers:
- Quantity verification — the number of cartons and units matches the purchase order
- Visual and finish check on the sample drawn according to AQL
- Basic functional testing (power-on, mechanism, sealing — depending on the product)
- Measurement and weight check against specifications
- Packaging check — carton, labeling, barcode, transport durability
- Dated photos of the inspected sample and the overall batch
An inspection report without dated photos of the actual goods proves nothing — any generic PDF could be recycled from a previous order.
Who performs the inspection
The major third-party agencies (SGS, Bureau Veritas, Intertek, TÜV, QIMA) offer standardized AQL inspections, billed per day per inspector. They are reliable but rigid in their report format. An independent local inspector often costs less and can be more responsive on short deadlines — provided you verify their credentials and give them a detailed written specification. The quality of any inspection depends entirely on how clear the brief is beforehand, regardless of who carries it out.
What to decide before you order, not after
The single biggest cause of disputes is not technical — it’s the lack of a written agreement on the rejection threshold before production starts. Three things to put in writing in the purchase order or proforma invoice:
- The accepted AQL level for major and minor defects, and what triggers a lot rejection
- Who pays for the inspection and who has the right to request it
- What happens if the inspection fails — rework, price reduction, or shipment refusal
Without this, an unfavorable inspection report becomes an improvised negotiation rather than an already-agreed contractual clause.
Where this fits into your project
Quality control is not an isolated step — it only makes sense as part of a bigger picture: supplier verification upfront, followed by on-the-ground production coordination and inspection. This is exactly what our sourcing support in Guangzhou covers — we set the criteria with you before the order, follow production, and are on-site for the pre-shipment inspection. Have a question about a current quality control process? Contact us.