Certificate of Conformance (CoC): what it is and how to write one
What a Certificate of Conformance is, when it’s required, and exactly what a CoC must state, plus a reusable structure suppliers can standardize across every shipment.
A Certificate of Conformance (CoC), sometimes called a Certificate of Conformity or a Certificate of Compliance, is a short, signed statement in which a supplier certifies that the products or materials in a shipment meet the requirements they were purchased against. It is one of the most common quality documents in manufacturing, and one of the easiest to get subtly wrong. This guide covers what a CoC is, when customers require one, exactly what it should contain, and how to standardize the format so every shipment goes out with a correct certificate.
What a Certificate of Conformance actually certifies
A CoC is a declaration, not a test report. It states that the identified products conform to a defined set of requirements (a purchase order, a drawing, a specification, a standard, or a contract) as of the shipment it accompanies. It does not, on its own, list measured results; that is the job of a Certificate of Analysis or an inspection report. The value of a CoC is traceability and accountability: it ties a specific lot or shipment to a named requirement and a responsible signatory.
In metals and many industrial supply chains, this maps to the inspection-document types defined in EN 10204. A Type 2.1 document is a “declaration of compliance with the order” with no test results, essentially a basic CoC. A Type 3.1 document adds actual test results validated by the manufacturer’s quality function. Knowing which type your customer expects avoids the common mismatch of sending a bare declaration when the contract required results.
When a CoC is required
You’ll be asked for a Certificate of Conformance whenever a customer needs documented assurance without necessarily needing every measurement:
- As a standing requirement on a purchase order or quality agreement
- For distributed or resold product, where the reseller passes through the manufacturer’s conformance
- In regulated or safety-critical supply chains (aerospace, automotive, medical, defense) as part of the receiving-inspection record
- For each lot or shipment of a production part, alongside first-article and PPAP evidence where those apply
What a Certificate of Conformance should include
A defensible CoC identifies the product, the requirement, and the responsible party unambiguously. At minimum:
| Field | Why it matters |
|---|---|
| Supplier and customer | Who is certifying, and to whom |
| Product identification | Part number, description, and revision |
| Quantity and lot / batch / serial | Exactly what the certificate covers |
| Purchase order / contract reference | The agreement the product is certified against |
| Requirements met | The drawing, specification, or standard(s) conformed to |
| Statement of conformance | A clear sentence certifying conformity |
| Authorized signatory and date | A named, accountable person and the issue date |
A CoC certifies conformance to a stated requirement, so the requirement has to be stated. “Conforms to specification” means little without the specification’s number and revision.
CoC vs Certificate of Analysis
The two are frequently confused. A Certificate of Conformance asserts that requirements are met; a Certificate of Analysis reports the specific characteristics that were tested and the results obtained. If your customer needs to see the numbers (chemistry, dimensions, performance), they want a CoA. If they need a traceable assertion of compliance, they want a CoC. Our side-by-side comparison breaks down when each applies.
Standardizing the CoC so it’s always correct
Because a CoC repeats the same structure for every shipment and changes only the product, lot, and reference fields, it is an ideal document to standardize once and reuse. Building it from a controlled template, rather than editing a copied Word file each time, keeps the statement wording, the required fields, and the layout consistent, so the only things that change are the values that should change. That is exactly the discipline behind standardizing product documentation across a company, applied to a compliance-sensitive document.
Whatever tool you use, treat the CoC as a controlled document: fixed structure, mandatory fields, a named signatory, and a version history. DataSheets Pro provides a structured starting point for certificates like this, but you remain responsible for verifying that the requirements you cite and the format you follow are current for your customer and industry.
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