Guide · Dates
Retest date vs expiry date on a certificate of analysis
- Short answer
- An expiry date is the date after which a material should not be used, based on stability data under stated storage conditions. A retest date is the date by which it should be re-examined to confirm it is still suitable. A CoA shows one or both, depending on the product and supplier practice, so read the label printed beside the date.
General background, not regulatory or GMP advice. Whether material may be used after either date is decided by your quality system and the rules that apply to you.
Two dates, two different promises
ICH Q7, which covers active pharmaceutical ingredients, defines an expiry date as the date after which the material should not be used, and a retest date as the date when it should be re-examined to ensure it is still suitable for use. It bases both on stability data and notes that common practice is to use a retest date, not an expiration date. Suppliers of other materials often, though not always, use the terms the same way.
In practice the choice follows the product. Finished drug products and many foods carry an expiry or best-before date, while chemicals, excipients and active ingredients more often carry a retest date. A certificate may print both, or a shelf life in months and no date at all. Food and pharmaceutical certificates often differ here: see food ingredient vs pharma CoAs. Other header fields are covered in CoA required fields.
Checking the dates on a certificate
Six checks that take a minute.
Find every date and its label
List the manufacture, analysis, issue, retest and expiry dates exactly as labelled. A date with no label needs a question to the supplier.
Decide which kind of date it is
Expiry, Use by, Best before and Valid until all set an end to use. Retest means re-examine by that date. A line such as 'valid for 24 months' needs a start point.
Check the start and the arithmetic
If only a shelf life in months is given, confirm which date it counts from, usually manufacture, and work out the date yourself.
Check the format
03/04/2026 is 3 April in some countries and 4 March in others. Look for a month name, an ISO date such as 2026-04-03, or another date on the certificate that settles it.
Compare with your terms
Many buyers set a minimum remaining shelf life at receipt in their purchasing terms. Check the time left against yours, as part of the review checklist.
Match the label and the storage conditions
The container label and the certificate should show the same date, and a date only holds if the material is stored as stated. Note any in-use period after opening.
Retest date and expiry date compared
Typical meanings. Check the supplier's own definitions.
| Question | Retest date | Expiry date |
|---|---|---|
| What it says | Re-examine the material by this date | Do not use the material after this date |
| Rests on | Stability data and a retest programme | Stability data under stated storage conditions |
| Often printed for | Chemicals, excipients, active ingredients | Finished products and many foods |
| At the date | Retest; if it still meets its specification, a new date may be assigned under a procedure | Use normally stops; any exception is a quality decision |
| Who can move it | Whoever holds the data and the authority, often the manufacturer | Typically only the manufacturer, with data |
| What to record | The date, the word 'retest', any retest result | The date and the word 'expiry' |
| Common mistake | Read as a hard stop, or ignored | Read as a retest date and used past it |
What goes wrong with dates
- One kind of date read as the other. Treating a retest date as an expiry wastes good material. Treating an expiry as a retest date uses material beyond its supported life.
- A date with no label. Manufacture, analysis, issue and expiry dates look alike. Ask rather than assume.
- Day and month swapped. 04/03/2026 changes meaning with the country of the issuer.
- Counting from the wrong start. Twenty-four months from manufacture is shorter than twenty-four months from receipt.
- Dates that disagree. The certificate, the container label and the delivery note should show one date for one lot.
- A retest date that moves. A re-issued certificate with a later date needs the retest result or stability basis behind it.
How CertiClean helps
CertiClean reads the manufacture date and the expiry or retest date from the header and keeps which kind of date it is (retest, expiry, best before, use by) with the value, so a retest date is not shown as an expiry. If both are printed, the expiry date is kept and the other is noted as also printed. A date it cannot read unambiguously, such as 03/04/2026, is kept as printed and flagged, and a shelf life given only in months is not turned into a date. See CoA to Excel and pricing.
Free allowance: 1 file per day, up to 10 pages, no account.
Questions people ask
What is the difference between a retest date and an expiry date?
An expiry date is the date after which a material should not be used. A retest date is the date by which it should be re-examined to confirm it is still suitable. Both normally rest on stability data and defined storage conditions.
Can I use material after its retest date?
Typically only after a satisfactory retest, done under the supplier's or your own procedure. Your quality system decides what is tested and who approves continued use.
Can I use material after its expiry date?
An expiry date marks the end of the period the supplier can support. Many quality systems do not allow use past it, and rules differ by jurisdiction and product. Treat any exception as a quality decision, not a purchasing one.
Why does my CoA show only a retest date?
Retest dates are common for chemicals, excipients and active ingredients. ICH Q7, which covers active pharmaceutical ingredients, notes that common practice is to use a retest date, not an expiration date.
What if the CoA gives only a shelf life, such as 24 months?
Ask the supplier which date it counts from, usually the manufacture date, and work out the date yourself. Record the result and your assumption, and ask for a dated certificate if you need one.
Is best before the same as an expiry date?
Not necessarily. In food labelling, best before usually relates to quality and use by to safety, though rules differ by country. On an ingredient CoA, ask what the supplier means.
Who can extend a retest date?
Typically whoever holds the supporting stability data and the authority under a written procedure, often the manufacturer. A buyer may retest and extend under its own procedures where allowed.
How should I record these dates?
Record each date and its label as printed, in an unambiguous format such as 2028-03-31, with the lot number and the storage conditions. Keep the certificate with the record.