Who decides what is on it
A certificate of conformity, or CofC, is your signed statement that what is in the box meets what was ordered. It is one of the most common documents in UK manufacturing and one of the least standardised.
There is no single UK regulation that fixes its content for machined parts. Your customer decides, through their purchase order terms and quality requirements. So the first step is always the same: read what the order actually asks for.
Two references come up often:
- AS9100, where the customer wants evidence of conformity and traceability with the delivery.
- DEFCON 627, which the Ministry of Defence uses where it requires a certificate of conformity, and which a prime may pass down to you with defence work.
If either is on your order, the order, not this article, is the authority.
One thing it is not: the UKCA or CE declaration of conformity. That is a statutory document for regulated finished products placed on the market. A CofC for machined parts made to a customer's drawing is a commercial document between you and your customer.
What customers usually expect
Across aerospace, defence and general precision engineering in the UK, a CofC normally shows:
- your company name and address
- a unique certificate number
- the customer's name and purchase order number, and the line if there are several
- the part number, description and drawing issue
- the quantity
- batch or lot numbers, and serial numbers where parts are serialised
- the specifications and standards the parts were made to
- reference to any concession or deviation that applies
- a clear statement that the goods conform to the order
- the name, position and signature of the person authorised to sign, and the date
What usually goes with it
The certificate is often the top sheet of a small pack:
- Material certificates, typically to BS EN 10204, most often type 3.1, carrying the heat number (also called the cast number) of the material you used
- Special process certificates from your approved suppliers: heat treatment, plating, anodising, NDT
- Inspection or first article reports, where the order calls for them
The pack only works if every document points at the same batch. A material cert with a heat number that cannot be tied to the parts in the box proves nothing.
The three mistakes customers reject
- The wrong drawing issue. The parts are right, the paperwork names the old issue, and the delivery is rejected at goods-in.
- A concession that is not mentioned. If the customer agreed to accept something outside drawing, the certificate should say so and quote their reference.
- A signature with no authority behind it. Customers may ask who is allowed to sign. Keep a short list, and keep it current.
Stop typing them
A CofC typed from memory is a CofC waiting to be wrong. Everything on it already exists somewhere in the job: the order, the drawing issue, the batches issued, the heat numbers, the subcontract certs, the serials, any concession.
If those records are captured as the work happens, the certificate can be produced from them when the despatch is confirmed, and it will agree with the delivery note because both come from the same place. The person signing is then checking a document, not writing one.
A quick check before it leaves
- Does the drawing issue match the order?
- Do the batch and serial numbers match the labels on the parts?
- Is every cert in the pack traceable to those batches?
- Are concessions referenced?
- Is it signed by someone authorised, and dated?
Five questions, a minute each, and far fewer rejected deliveries.