Certificate of conformity vs certificate of analysis: what each one tells you

A certificate of conformity (CoC) is a signed statement from a manufacturer or supplier that a product meets a stated specification or standard, usually without test data. Laboratory materials often arrive with paperwork, and the CoC and the COA are two of the most common documents, with similar names. A certificate of analysis (COA) shows the measured results for one lot. Both are useful, but they don't carry the same weight. This guide explains what each one is, how they differ, and what to look for in each.

Terms are defined in the glossary.

What is a certificate of conformity?

A certificate of conformity is a document in which a manufacturer or supplier states that a product meets a particular specification, standard or set of requirements. It is also called a certificate of compliance, and is often shortened to CoC or CofC.

A typical certificate of conformity names:

• the product, and often its part number or catalogue number,
• the lot, batch or serial number, or the order it covers,
• the specification or standard it conforms to,
• a statement that the product meets it, and
• the name, role and signature of the person making the statement, with a date.

What it usually doesn't include is data. It tells you the supplier has checked the product against its specification. It doesn't show you what was measured or how.

Certificates of conformity are common for manufactured goods and consumables: glassware, plastic tubes, filters, vials, stoppers and components. For those items the specification is mostly about dimensions, materials and manufacturing controls, and a statement of conformity is often what buyers need.

Declarations of conformity for regulated products

A declaration of conformity is a related but more formal document. For products covered by product safety law in Great Britain, such as electrical equipment and machinery, the manufacturer must draw one up before applying a UKCA or CE mark. It names the laws and standards the product meets and is a legal statement by the manufacturer.

That legal declaration is different from the everyday certificate of conformity a supplier sends with an order. When someone asks for a "certificate of conformity", it is worth checking which they mean.

A vehicle certificate of conformity is a different document again: the vehicle maker's statement that a vehicle was built to type-approval standards, which the DVLA can ask for at first registration (GOV.UK). It has nothing to do with laboratory materials.

What is a certificate of analysis?

A certificate of analysis is issued for one production lot. It lists each test, the method used, the specification and the result. For a synthetic peptide, the key tests are usually identity by mass spectrometry and purity by HPLC.

Because a COA reports results, you can judge it for yourself. You can check that the result meets the specification, that the method suits the test and that the figures are internally consistent. See how to check a certificate of analysis.

Certificate of conformity vs certificate of analysis

The difference comes down to evidence. A certificate of conformity asks you to trust the issuer's checks. A COA shows you the checks. For a material whose quality depends on chemistry, such as a peptide, the results matter, so a COA is the document to ask for.

Some documents combine the two: a COA that also states "the lot conforms to specification" at the bottom. That is common and perfectly sound, because the statement is backed by the results above it.

Graded inspection documents

Some industries make the difference explicit. In metals, for example, the European standard EN 10204 sets out four types of inspection document (Van Leeuwen):

A request for an "EN 10204 3.1 certificate" is therefore a request for lot-specific results, checked by someone outside production.

Laboratory chemicals don't follow that standard, but the same scale is a useful way to think about any document:

1. A statement that the product meets its specification.
2. Typical results for the product in general.
3. Results for the specific lot you received.
4. Results for the specific lot, from an independent laboratory.

Each step up gives more evidence. A lot-specific COA sits at step 3. Independent testing is step 4. See peptide purity testing in the UK for how that works.

What to check on a certificate of conformity

• The specification it names. "Conforms to specification" means little unless you know which specification, and can see it.
• The lot or order number. It should match what you received.
• Who signed it, and their role. A named quality role carries more weight than an unsigned form.
• The date. It should fall after the product was made and before it shipped.

If a certificate of conformity is all you have for a chemical, ask whether a lot COA is available.

Data integrity and ALCOA

Every certificate is only as good as the records behind it, which regulators judge against principles known as ALCOA (attributable, legible, contemporaneous, original, accurate). They are explained, with the extended ALCOA+ list, in QA vs QC: records and data integrity, and they are why a COA with a chromatogram, a report number and a dated sign-off is more convincing than a headline figure alone. See also lot numbers and traceability.

Related guides

For reading a COA line by line, see what a certificate of analysis tells you. For spotting problems with a COA, see how to check a certificate of analysis. For how to judge the numbers on one, see accuracy, precision and significant figures. Every lot has its own COA, published on the product page and on that lot's own page. See Quality.