What is a batch or lot number?

An identifier for one production run of a product. Material made in the same run shares a batch number, which is how a test result for one sample can be linked to the other vials from that run.

Why can’t the laboratory confirm that my vial is the tested batch?

The laboratory only knows what it was sent and what the client wrote on the sample. It has no way of knowing whether the vial you hold came from the same run, so the link rests on the labelling and the seller’s records.

What should I compare between the vial and the report?

The batch or lot number and the product name, character for character, plus the declared amount. Then check the dates make sense: the batch should exist before the test, and the test should be recent enough to be relevant.

Batch and lot numbers: linking a COA to the vial you hold

By PeptideProof · Updated 13 October 2026 · 5 min read

A COA is evidence about a tested sample. What makes it evidence about your product is the batch number — the link between the report and the vial. It is also where the chain is most often weak, because nobody independent checks it.

How the link works

A manufacturer makes a production run and gives it a batch (lot) number. Vials from that run carry the number. A sample from the run is sent for testing, labelled with the same number, and the report repeats it. If the numbers match and the paperwork is honest, the result describes the run.

Where it can break

The sample isn’t from the run. The laboratory records the label it’s given. It can’t tell whether the sample was drawn from the production run it names.
The label on the vial doesn’t match any report. A report may exist for a neighbouring batch, or for a product code instead of a batch.
One report is shared across batches. Reusing a report for several runs, deliberately or sloppily, leaves later batches without evidence of their own.
Dates don’t fit. A report dated before a batch could have existed, or a very old report for a recent run.

What to check

Read the batch number on the vial and on the report, character for character. Look at similar-looking characters (0/O, 1/I).
Check the product name and declared amount agree too.
Compare the dates: is the test after the batch was made and recent enough to matter?
Ask whether the seller has a separate report for each batch, and whether the laboratory can confirm the report (more on verifying).
Some reports include photographs of the received sample; compare them with what you have.

How PeptideProof treats the batch

It reads the batch number from the document and notes whether that batch is already on record. A batch with no other evidence is shown as “not yet associated with other evidence”, and the physical link between a vial and a report is marked as not checked, because it can’t be established from a document alone.

Frequently asked questions

What is a batch or lot number?: An identifier for one production run of a product. Material made in the same run shares a batch number, which is how a test result for one sample can be linked to the other vials from that run.
Why can’t the laboratory confirm that my vial is the tested batch?: The laboratory only knows what it was sent and what the client wrote on the sample. It has no way of knowing whether the vial you hold came from the same run, so the link rests on the labelling and the seller’s records.
What should I compare between the vial and the report?: The batch or lot number and the product name, character for character, plus the declared amount. Then check the dates make sense: the batch should exist before the test, and the test should be recent enough to be relevant.

See it on a real document

PeptideProof reads a COA for you and shows what is only reported, what has no evidence and what looks inconsistent. See an example first, or check your own — new accounts include free analyses.

See an example report Verify a COA

More guides

Educational information about reading laboratory documents. It is not medical, dosing or purchasing advice, and it doesn’t say that any product is safe, legal or suitable for any use. See the medical and research-use disclaimer.