Business document
Certificate of Conformity (CoC)
The supplier's signed statement that what was delivered meets what was specified. It is a claim about the goods, made by the person who made them, and it travels with the delivery.
Also called: Certificate of conformance · CofC · Conformity certificate · Declaration of conformity (a different thing)
- Who sends it
- The supplier's quality function, or despatch under quality's authority, travelling with the goods.
- Who receives it
- The customer's goods-in and quality functions, who file it against the delivery and the batch.
- When it is used
- With each delivery where certification is a contractual requirement — routine in aerospace, automotive, medical, defence, rail, oil and gas, and increasingly common in general engineering.
- Does it bind anyone
- It is a contractual representation about the goods rather than a regulatory approval, and a false one has consequences ranging from rejection and recovery of costs to fraud in regulated sectors. It is distinct from a declaration of conformity, which is a manufacturer's regulatory statement — a CE or UKCA declaration, for instance — made against legislation rather than against a customer's purchase order.
What it is
A certificate of conformity is a signed statement from the supplier that the goods being delivered conform to the specification they were ordered against — the drawing at its stated revision, the material grade, the applicable standards, the processes required.
It is a claim, not evidence. A CoC asserts conformity; it does not by itself prove it. What makes it meaningful is that it is signed by someone with authority, that it identifies exactly which goods it covers, and that the records supporting it exist and can be produced.
Its practical function in the chain is to let the customer's goods-in accept the delivery without re-inspecting it. That is why a delivery arriving without a required CoC is normally rejected even when the parts are perfect — receiving has no authority to accept it, and the parts pay the freight home.
Every field explained — 20 in total
What each field means, a realistic example value, whether you can leave it out, and the thing that goes wrong with it in practice.
| Field | What it means | Example | Needed? |
|---|---|---|---|
| Certificate number | Unique reference for this certificate.Watch out Should be traceable in both directions — to the delivery note that carried it and to the works order and inspection records behind it. | CoC-58117 | Required |
| Issue date | When the certificate was issued. | 17 April 2026 | Required |
| Supplier name, address and approvals held | Who is making the statement, and under what quality approvals.Watch out Quote the approval number and its scope, not just the standard. An ISO 9001 certificate whose scope excludes the process in question is a common finding in supplier audits. | Rochdale Precision Ltd — ISO 9001:2015, certificate FM 664120 | Required |
| Customer name and delivery address | Who the goods were supplied to. | Northgate Engineering, Sheffield S9 | Required |
| Customer purchase order number | The order the goods were supplied against.Watch out Without it, goods-in cannot connect the certificate to the delivery, and a certificate that cannot be matched is treated as absent. | PO 4500-887-2261, line 010 | Required |
| Delivery note number | The consignment this certificate covers. | DN-58117 | Required |
| Part number and description | What the certificate covers, in the customer's numbering. | NG-44821 — Mounting bracket LH | Required |
| Drawing number and revision | The exact engineering definition conformity is claimed against.Watch out Certifying against a revision other than the one on the purchase order is worse than sending no certificate at all — it is a documented statement that you made the wrong thing. | NG-44821 revision D | Required |
| Specification and standards conformed to | The material, process and test standards the goods meet.Watch out List the standard and its revision or year. Standards get superseded, and 'conforms to ISO 7599' without a year is a claim that ages badly. | Material AA 6082-T6 to BS EN 573-3; anodised to BS EN ISO 7599 Class 15µm, natural | Required |
| Quantity certified | How many units this certificate covers.Watch out Must match the delivery note quantity. A certificate for 400 accompanying a delivery of 388 is a discrepancy that goods-in will raise, and it delays the receipt. | 388 | Required |
| Batch, lot, heat or cast numbers | Traceability identifiers linking the goods to their material and process records.Watch out The heart of the document. Without batch identity a certificate certifies nothing in particular, and a later defect means containing everything rather than one batch. | Batch 26-0412-A, material cast 8841-C | Required |
| Serial numbers | Individual item identifiers where the parts are serialised. | Serials RP-44821-0412 to RP-44821-0799 | Conditional |
| Material certificate reference | The mill certificate for the raw material, referenced or attached.Watch out A CoC is your statement; a mill certificate is the material producer's. Where a customer requires EN 10204 type 3.1 or 3.2 material certification, your CoC does not substitute for it. | Mill cert 3.1 to BS EN 10204, ref MC-8841-C attached | Conditional |
| Processes performed and by whom | Which operations were carried out in house and which were subcontracted.Watch out Where a customer maintains an approved process source list, using an unapproved subcontractor invalidates the delivery regardless of the result. Naming them makes it visible rather than discoverable. | Machined in house; anodising by Pennine Finishing Ltd (approved supplier 214) | Conditional |
| Inspection results or reference to them | Key measured characteristics, or a reference to the inspection record.Watch out Where the customer asks for actual results, generic 'inspected and found conforming' wording will be rejected. Where they do not, referencing the record is enough — but the record has to exist. | Critical dim. 46.00 ±0.05 — measured range 45.98–46.02, n=20. Report IR-58117. | Conditional |
| Measuring equipment and calibration status | That the equipment used was in calibration.Watch out One of the most common audit findings. A perfect inspection result taken on an out-of-calibration instrument is not a result. | CMM asset 0117, calibrated 12 Feb 2026, due 12 Feb 2027 | Conditional |
| Concessions and deviations | Anything supplied that does not fully conform, with the authority for it.Watch out 'None' must be stated explicitly rather than left blank. Shipping non-conforming goods under an unrecorded concession is the failure that turns a delivery into a claim. | None. (Or: Supplied under customer concession CN-2026-014, dated 9 April 2026.) | Required |
| Statement of conformity | The actual declaration.Watch out Read the wording you are signing. Blanket phrases like 'conform in all respects' are broader than most companies intend and broader than most inspection plans support. | We certify that the goods described above have been manufactured, inspected and tested in accordance with the requirements of the above purchase order and drawing, and conform in all respects. | Required |
| Authorised signatory — name, position, signature | The person taking responsibility, with the authority to do so.Watch out It should not be despatch, and it should not be a scanned signature applied automatically by a template. The named individual is the point of the document. | K. Ferreira, Quality Manager | Required |
| Retention period for supporting records | How long the underlying records will be kept and available.Watch out Often specified contractually in aerospace, medical and rail. Agreeing to a retention period you do not actually operate is a finding waiting to be made. | Supporting records retained 11 years | Optional |
A filled-in example
Realistic values throughout — the sort of document that would actually pass through a business.
Certificate of Conformity CoC-58117
- Certificate number
- CoC-58117
- Date
- 17 April 2026
- Supplier
- Rochdale Precision Ltd — ISO 9001:2015, cert FM 664120
- Customer
- Northgate Engineering, Sheffield S9
- Purchase order
- 4500-887-2261, line 010
- Delivery note
- DN-58117
| Part | Drawing / rev | Qty | Batch | Material cast | Specification |
|---|---|---|---|---|---|
| NG-44821 | NG-44821 rev D | 200 | 26-0412-A | 8841-C | AA 6082-T6, anodised 15µm natural |
| NG-44821 | NG-44821 rev D | 188 | 26-0415-B | 8841-C | AA 6082-T6, anodised 15µm natural |
- Processes
- Machined in house; anodising by Pennine Finishing Ltd (approved supplier 214)
- Inspection
- Report IR-58117. Critical dim 46.00 ±0.05 — measured 45.98–46.02, n=20. CMM asset 0117, cal. due 12 Feb 2027.
- Material certification
- EN 10204 type 3.1 mill certificate MC-8841-C attached
- Concessions
- None
- Certified by
- K. Ferreira, Quality Manager
What happens next
- 01Goods-in check that a certificate is present, that it matches the delivery note and purchase order, and that the quantity and revision agree.
- 02The certificate is filed against the customer's goods receipt and, in regulated sectors, against the batch for the life of the product.
- 03Where the customer performs receiving inspection, the certificate may reduce or remove the need for it.
- 04A missing, mismatched or unsigned certificate normally results in the delivery being quarantined or rejected, regardless of the condition of the parts.
- 05If a defect is found later, the certificate and its batch numbers define the scope of containment.
Where it appears in the chain
- Planning and making itTurning an accepted order into a scheduled job, materials, machine time and finished parts — and reporting honestly when the date is going to move.
- Despatch and shipmentPicking, checking, packing, documenting and sending the goods — and capturing the proof of delivery that the invoice will later depend on.
Common mistakes
MistakeThe certificate does not travel with the goods
Why it happens: It is produced by quality and the delivery is packed by despatch, and the two steps are not linked.
What to do instead: Make certification a flag on the order line that blocks despatch until satisfied. Perfect parts rejected for missing paperwork pay freight both ways and count as a late delivery.
MistakeCertifying against the wrong drawing revision
Why it happens: The template pulls the latest revision on file rather than the one on the purchase order.
What to do instead: Take the revision from the order, and check it against the works order. Certifying the wrong revision is a documented statement that the wrong part was made.
MistakeGeneric wording with no batch identity
Why it happens: One certificate template is used for every delivery and the batch field is optional.
What to do instead: Batch or lot numbers are mandatory. A certificate without them cannot support containment, which is the main reason the document exists.
MistakeSigned automatically by a template
Why it happens: It is faster and the signature is on file as an image.
What to do instead: A named person with delegated authority signs, having seen the inspection record. An automatic signature is the whole document reduced to decoration.
MistakeConfusing a CoC with a material certificate
Why it happens: Both are 'certificates' and both mention the material.
What to do instead: A CoC is your statement about the finished goods. An EN 10204 3.1 or 3.2 mill certificate is the material producer's statement about the raw material. Where the customer requires the latter, yours does not substitute for it.
MistakeNot stating 'none' under concessions
Why it happens: There were no concessions so the field is left blank.
What to do instead: State it explicitly. A blank field is ambiguous, and ambiguity in a certificate is exactly what audits are designed to find.
Terminology
- Declaration of conformity
- A manufacturer's regulatory statement that a product meets applicable legislation — a CE or UKCA declaration, for example. Different in purpose and audience from a customer CoC.
- EN 10204 type 3.1
- A material certificate issued by the manufacturer's authorised inspection representative, with actual test results. Type 3.2 adds independent verification.
- Concession
- Written authority, usually from the customer, to supply something that does not fully meet the specification.
- Traceability
- The ability to link a delivered item back to its material, processes, equipment and inspection records — normally through batch or serial numbers.
- First article inspection
- A full dimensional and specification verification of the first part from a new process, reported separately and usually approved before production runs.
- Approved supplier list
- The customer's register of sources permitted for particular processes. Using an unlisted subcontractor invalidates the delivery regardless of quality.
Common questions
›What is the difference between a certificate of conformity and a declaration of conformity?
A certificate of conformity is a supplier statement to a customer that specific goods meet a specific purchase order and drawing. A declaration of conformity is a manufacturer's statement to the market that a product meets applicable legislation — the basis of CE and UKCA marking. Different audiences, different obligations, and one does not substitute for the other.
›Does a certificate of conformity prove the parts are good?
No. It states that they conform, on the authority of the person who signed it. What supports the claim is the inspection record, the calibration status of the equipment, and the batch traceability behind it. A certificate with nothing behind it is a signature on a template.
›Who should sign a certificate of conformity?
A named individual with delegated quality authority who has seen the inspection evidence — typically the quality manager or an approved signatory. Not despatch, and not an image applied automatically by a document template.
›What happens if goods arrive without a required certificate?
They are usually quarantined or rejected outright, because receiving has no authority to accept uncertified goods. The parts are then returned or held at the customer's site pending paperwork, freight is paid twice, and the delivery counts as late — all for a document that takes minutes to produce.
›Is a certificate of conformity legally required?
Rarely by law, and very often by contract. In aerospace, automotive, medical, defence, rail and energy it is effectively mandatory through the purchase order and the customer's quality requirements. Where it is contractual rather than statutory, a false certificate is still a serious matter — it is a misrepresentation about goods someone else will rely on.
›How long should the supporting records be kept?
As long as the contract requires, which in regulated sectors can be a decade or more and occasionally the life of the product. Agree the period explicitly, and make sure the retention you promise is the retention you actually operate.
Tools for this
Downloadable, self-contained, and yours to keep — they run in a browser with no account and no data leaving your machine.
- Certificate & Test Record RegisterProKeep a register of every certificate and test record your business issues — electrical, gas, pressure, lifting, alarms — with expiry and retest tracking, failure rates and a printable report. Runs entirely in your browser — nothing is uploaded.
- Batch & Lot Traceability LogFreeLink incoming material batches to the batches you make and the customers you send them to, so a recall can be scoped in minutes instead of days. Runs entirely in your browser — nothing is uploaded.
- Calibration RegisterFreeKeep every measuring instrument in one calibration register: intervals, next due dates, certificates, traceability and as-found results, with overdue warnings and a printable audit report. Runs entirely in your browser — nothing is uploaded.
Reviewed 2026-08-15. Nothing here is legal, tax or accounting advice — the mandatory content of commercial and tax documents varies by jurisdiction, so confirm the specifics for where you trade.