A supplier audit should determine whether a manufacturer can repeatedly meet your requirements, not merely whether it owns the right certificate. A practical supplier audit checklist combines system evidence with observation of the actual processes, people, equipment and records that will support your product.
The checklist below is designed for new-source approval, periodic review or a risk-based reassessment after performance concerns.
1. Audit scope and preparation
Define the site, processes, products and risks included. Review the RFQ, drawings, certifications, questionnaire, previous performance and open issues before the visit. Identify critical processes and subcontractors.
Send an agenda and request representative records, but retain the freedom to follow evidence on the shop floor. The audit team should include technical and quality knowledge relevant to the work.
2. Organisation and responsibilities
- Are responsibilities for production, quality and release clear?
- Is there an independent route to stop or reject non-conforming work?
- Are competent deputies available for key roles?
- How are customer requirements communicated to operators?
Interview people who perform the process, not only managers. Their understanding often reveals whether documented procedures are actually used.
3. Quality management and document control
- Are procedures, drawings and work instructions revision controlled?
- Can the supplier prove that obsolete versions are removed?
- Are records legible, traceable and retained for an agreed period?
- Are internal audits and management reviews effective?
A certification can support the assessment, but it does not replace product-specific evidence.
4. Technical review and contract review
Check how the supplier reviews drawings, materials, tolerances, volumes, tests, packaging and delivery before acceptance. Open questions should be documented and resolved. Changes to customer information must reach planning, production and inspection.
For complex custom parts, compare the process with the framework to qualify technical manufacturing suppliers. Where European market requirements apply, also review the European supplier quality requirements checklist.
5. Equipment and process capability
- Does the site have the intended equipment and capacity?
- Are maintenance and setup controls effective?
- Are key process parameters defined and recorded?
- Are special processes validated where output cannot be fully verified later?
- Are tools, fixtures and programmes protected from unauthorised changes?
Observe a live or comparable job. A clean facility is positive, but consistent process control matters more than presentation.
6. Material and traceability
Follow one material lot from receipt through production, inspection and shipment. Verify identification, segregation, status and certificate linkage. Check how substitutes or deviations are approved.
For parts with regulatory or safety implications, ensure traceability reaches the required level and survives subcontracted operations.
7. Inspection and calibration
- Are inspection plans linked to current requirements?
- Can the equipment measure tolerances with suitable accuracy?
- Is calibration status visible and current?
- Are first-off, in-process and final results recorded?
- How are non-conforming results contained?
The supplier quality inspection plan guide helps translate audit findings into product controls.
8. Non-conformance and corrective action
Review recent internal and customer complaints. Look for containment, root-cause analysis, implemented actions and verification of effectiveness. Repeated “operator error” conclusions may indicate weak analysis.
Confirm that suspect stock and shipped material can be identified quickly. The escalation route should be clear outside normal working hours where disruption would be severe.
9. Capacity, planning and delivery
Assess current utilisation, bottlenecks, shift structure, workforce flexibility and dependency on single machines or people. Review how forecasts become production plans and how late work is escalated.
Capacity claims should be supported by cycle times, yields and available hours. Ask what happens if demand rises or a critical machine fails.
10. Sub-suppliers and continuity
Identify subcontracted processes and verify how they are approved, specified and monitored. Evaluate business-continuity plans for utilities, IT, fire, labour, materials and logistics. Check whether customer-owned tooling and data can be recovered.
A broader offshore manufacturing risk assessment may be needed where distance and long recovery times increase exposure.
Scoring and follow-up
Use scores to support consistency, not to hide critical findings in an average. Classify findings by risk and define evidence required for closure. Supplier approval may be full, conditional or refused. Conditional approval should include limits, owners and deadlines.
Verify corrective actions through documents, samples or a follow-up visit. Connect audit results to sourcing decisions and ongoing supplier performance.
Conclusion
A supplier audit checklist is effective when it tests real capability, traceability and process control against product risk. Evidence from the factory floor should support every approval decision. TOS performs and coordinates supplier assessments as part of a controlled route from sourcing to series delivery.