Certificate of conformance: what it must include and how to issue one

A certificate of conformance (CoC) is a document in which a supplier or manufacturer certifies that the goods delivered conform to the requirements of the order — the drawing, the specification, the standard named in the purchase order. It is common in aerospace, defence, automotive, electronics and construction supply chains, and many buyers will not receive goods into stock without one. Its value depends on what sits behind the signature: a CoC is only as good as the inspection records it summarises.

What a certificate of conformance must include

• Supplier name, address and a unique certificate number.
• Customer name and the purchase order number, including revision.
• Part number, drawing number and revision, and a description of the goods.
• Quantity shipped and the lot, batch or serial numbers covered.
• The specifications or standards the goods conform to.
• A clear conformance statement, plus any approved deviations or concessions.
• Name, title and signature of an authorised person, with the date.

Certificate of conformance vs mill test report

The two are often requested together and often confused. A certificate of conformance is a statement: the goods meet the stated requirements. A mill test report (also called a mill test certificate or material test report) is evidence: it records the actual chemical composition and mechanical test results for a heat or batch of material, issued by the mill that produced it. Buyers of steel, pipe and fasteners typically want the material test report for traceability to the heat, and a CoC from their direct supplier covering the finished part.

If you are the supplier, never issue a CoC for requirements you have not verified. Where a characteristic comes from a sub-supplier, keep their certificate on file and reference it, so the chain of evidence holds up in an audit.

How to issue a CoC for every shipment

1. Build one controlled template with the required fields and your conformance wording.
2. Pull order, part and lot data from the shipment rather than retyping it.
3. Check that inspection records, including any first article inspection report, exist for the lot being shipped.
4. List approved deviations explicitly; if there are open non-conformances, do not ship under a clean CoC.
5. Have an authorised person sign, and send the certificate with the goods or ahead of delivery.
6. File the signed copy against the order and lot so it can be retrieved years later.

Ettex PDF handles the issue step: a fillable certificate template with fields for order, part, lot and quantity, signed electronically and saved as a locked PDF. Keeping one template per customer requirement avoids the most common audit finding — certificates missing the drawing revision or the lot numbers.

Certificate of conformance vs certificate of conformity

The terms are used interchangeably in many supply chains. In regulatory contexts, "certificate of conformity" often refers to a document tied to a market access scheme — for example a declaration that a product meets EU requirements, or a certificate issued by an inspection body for import into a particular country. Check which one the customer or regulator means before issuing.