Vetting a Chinese Supplier: A Practical Checklist
Short answer: vet a Chinese supplier in four stages — paperwork, capability proof, commercial terms, and a paid trial order. Request the business license and ISO9001 certificate, ask for a process capability report on your actual tolerance (not a generic brochure), confirm who owns the tooling, and run a 50–200 piece pilot before committing to volume. A real factory will answer within 12 working hours with a drawing-marked quote. BQUQ, a Dongguan source factory running CNC machining at ±0.005 mm alongside stamping, springs, and heat sinks, uses exactly this sequence with new buyers.
Most sourcing failures are not caused by a supplier lying outright. They are caused by a buyer asking the wrong questions in the wrong order, then discovering the gap eight weeks later when the first container arrives. This checklist is the sequence our own engineering team would use if we were the buyer — and it is the sequence we expect from serious customers.
Why does the order of vetting matter more than the checklist itself?
Because each stage filters for a different failure mode, and skipping ahead wastes time on suppliers that were never viable.
- Stage 1 — Legitimacy. Does the company legally exist, and is it the entity that will invoice you?
- Stage 2 — Capability. Can it hold your tolerance, on your material, at your volume?
- Stage 3 — Commercials. Who owns the tooling, who pays for scrap, what happens when a drawing changes?
- Stage 4 — Trial. Does reality match the samples and the paperwork?
A trading company can pass Stage 1 and fail Stage 2. A genuine factory can pass Stages 1 and 2 and still fail Stage 3 because nobody wrote down the tooling ownership. Stage 4 catches everything else.
Stage 1: What paperwork should you verify before anything else?
Start with three documents and cross-check them against each other.
| Document | What to check | Red flag |
|---|---|---|
| Business license (营业执照) | Unified social credit code, registered capital, scope covering your process, registered address | Scope lists only "trading" or "import/export" |
| ISO9001 certificate | Certificate number, issuing body, expiry date, scope wording | Expired, or scope names a different product category |
| Factory address proof | Lease, utility bill, or a live video walk-through | Address differs from the license, no explanation |
Verify the ISO9001 certificate number with the issuing certification body's online registry — not with a PDF the supplier emailed you. PDFs are trivially edited.
Ask directly: "Are you the manufacturer or a trading company?" Both answers are acceptable, but they change everything downstream. A trader adds margin and can be excellent for low-volume multi-process sourcing; a factory gives you direct engineering access and usually better tooling economics. What you cannot tolerate is a trader claiming to be a factory, because you will be negotiating capability you cannot actually audit.
The video walk-through test
Request a live, unscheduled video call — not a recorded factory tour. Ask the camera operator to walk to a specific machine and show the serial plate, then pan to the operator station and the in-process inspection bench. Recorded tours are professionally produced and prove nothing. A live call at 9 a.m. Dongguan time that reaches a running machine in under four minutes tells you more than twenty pages of brochure.
Stage 2: How do you prove a supplier can actually hold your tolerance?
Send a drawing with a tolerance at the edge of what you need, and ask for a process capability (Cpk) discussion — not just "yes, we can do it."
For CNC machining, ±0.005 mm is achievable on critical features in a controlled shop, but it is not achievable on every feature of every part. A competent supplier will tell you which dimensions they can hold comfortably, which need a secondary operation, and which are better relaxed. A supplier that says "no problem, all dimensions to ±0.005 mm" on a part with a 300 mm span is telling you they did not read the drawing.
| Capability question | Weak answer | Strong answer |
|---|---|---|
| Tolerance on critical feature | "Yes, we can" | Names the machine, fixture strategy, and inspection method |
| Material certification | "Standard material" | Offers mill certs with heat number traceability |
| First article inspection | "We check every part" | Describes FAI report format, sampling, and gauge list |
| Surface finish | "Good quality" | Quotes Ra value and the finishing process to reach it |
| Volume ramp | "No problem" | States cycle time, cavities, and tooling lead time |
For stamped parts, the equivalent question is about tooling: how many stations, what tonnage, and whether the die is designed for your annual volume or for a prototype run. For springs, ask about wire diameter tolerance, coiling method, and whether stress relief is in-line or batch. For heat sinks, ask about extrusion versus skiving versus die-casting — the process choice drives both cost and thermal performance.
If you are comparing process routes for a part that could be machined or stamped, our breakdown of CNC vs stamping supplier selection covers where the cost crossover sits.
Stage 3: Which commercial terms decide whether the relationship survives?
Technical capability gets you a good first shipment. Commercial clarity gets you a good fifth one.
Tooling ownership and transfer
This is the single most common source of dispute. Write it into the PO:
- Who pays for the tool, and what is the amortization schedule if it is billed per piece?
- Who owns the physical tool, and who owns the design files and electrode drawings?
- What is the buy-out price if you leave?
- Will the tool be stored at the supplier's site or a third party, and who pays storage?
A supplier that resists documenting tooling ownership is telling you something. Get it in writing before the first invoice.
Price structure transparency
Ask for a cost breakdown on one representative part: material, machining time, tooling amortization, finishing, inspection, packaging, and margin. You do not need to audit every line — you need to see whether the supplier understands their own cost drivers. A quote that is a single number with no structure cannot be negotiated rationally, and it cannot be re-quoted when your volume changes.
Change control and scrap liability
Define, in writing:
- How a drawing revision is priced and how long it takes to implement
- Who absorbs scrap when the defect is a supplier process failure versus a design issue
- What the rework policy is, and whether rework is allowed on safety-relevant features
Our supplier scorecard metrics guide gives you the KPIs to track once production starts — on-time delivery, PPM, and response time are the three that predict everything else.
Stage 4: What does a proper trial order look like?
A trial order is not a sample. Samples are hand-selected. A trial order is a production run on production equipment, with production fixtures, inspected and documented.
| Trial parameter | Typical recommendation | Why |
|---|---|---|
| Quantity | 50–200 pieces, or one full die/mold shot | Large enough to reveal process drift |
| Tooling | Production tooling, not soft tooling | Soft tooling hides capability gaps |
| Inspection | Full dimensional report + material cert | Gives you a baseline for future PPM |
| Packaging | Actual production packaging | Damage in transit is a real failure mode |
| Lead time | Quoted lead time, measured | Tests planning honesty, not just capability |
Pay for the trial. A supplier who offers a free trial order is usually absorbing the cost into your future unit price, and a free trial gives you no leverage if it fails.
If the trial passes, place a small volume order before the big one. If it fails, you have lost a few weeks and a modest tooling cost instead of a production line.
For parts where a defect is expensive to detect downstream, bring in a third party. Our notes on third-party inspection in China explain when the cost is justified and when in-house FAI is enough.
What should you do when the answers do not add up?
Treat inconsistency as the signal, not the individual answer.
- License address differs from factory address → ask for the lease and a live walk-through
- Certificate scope does not match your process → ask for the actual certificate, not the marketing sheet
- Quote arrives in under two hours with no questions → the supplier did not read the drawing
- Quote takes two weeks → the supplier is not prioritizing you, and will not prioritize your expedite request either
- Engineer refuses a technical call → you will be dealing with a salesperson for the life of the project
A supplier that answers slowly but accurately is generally a better long-term partner than one that answers instantly and vaguely. The exception is the initial quote: a shop with real engineering capacity can turn a straightforward RFQ around in 12 working hours because the estimator and the process engineer sit in the same building.
Frequently Asked Questions
Q: Do I need to visit the factory in person?
A: Not for every supplier, but for a primary supplier, yes — or send a trusted third party. A live video walk-through covers 70% of what an in-person visit reveals: machine condition, housekeeping, in-process inspection, and whether the floor is actually running your process. What a visit adds is scale verification and informal conversation with operators. Budget one trip before you commit to annual volume.
Q: Is ISO9001 enough to trust a Chinese supplier?
A: No. ISO9001 confirms a documented quality system exists and has been audited; it does not confirm the system is applied to your part. Verify the certificate number with the issuing body, then ask for a Cpk study or first article report on a comparable part. A supplier with a real system will produce these quickly. A supplier with a certificate on the wall will stall.
Q: How do I know if I am talking to a factory or a trading company?
A: Ask for the business license scope, the factory address, and a live video walk-through in the same message. Trading companies typically have a registered office address, a scope listing trade or import/export, and will offer to arrange a factory visit "at a partner site." Factories will simply show you the floor. Neither is automatically better — but you must know which you are buying from.
Q: What is a fair MOQ for a first order?
A: For CNC machining, 50–200 pieces is a reasonable trial MOQ and most capable shops will accept it. For stamping and springs, MOQ is driven by tooling, so the practical minimum is one production run. Flexible MOQ is normal at the trial stage; what matters is whether the supplier quotes honestly at that volume rather than padding the unit price to discourage you.
Q: How long should a quote take?
A: For a straightforward part with a clear drawing, 12 working hours is achievable from a factory with in-house estimating. Complex assemblies, multi-process parts, or drawings with missing tolerances legitimately take longer. If a quote arrives in 30 minutes with no clarifying questions, be suspicious — it usually means the supplier is guessing, and the guess will surface as a change order later.
Related Resources
- About BQUQ and our four production lines in Dongguan: /about/
- CNC machining to ±0.005 mm: /cnc-machining/
- Metal stamping and tooling: /custom-metal-stamping/
- Custom compression springs: /compression-springs/
- Industry trends in China sourcing: /industry-dynamics/
- More technical articles: /bquq-blog/
- Case studies: /case/
- Contact our engineering team: /contact/
Authored by the BQUQ Engineering Team. BQUQ (Dongguan) runs CNC machining (±0.005 mm), metal stamping, custom springs, and heat sink production in one ISO9001 factory. Source-direct from Dongguan, China — quote in 12 hours: sc@bquq.com | WhatsApp +86 13713157787 | www.bquq.com
