What a calibration certificate must contain under ISO/IEC 17025

What must every report carry?

ISO/IEC 17025 §7.8.2 applies to a test report, a calibration certificate and an inspection report alike. Paraphrased, the certificate must include:

A title

Calibration Certificate, or Inspection Report where the work is inspection, so the two are never confused.

The laboratory's name and address

And the location where the calibration was performed, if different, including a customer's site.

Unique identification

A number on every page, with each page recognisable as part of the whole and a clear end to the document: Page n of N.

The customer

Name and contact information.

The method

Identification of the procedure used, which has to be one the laboratory has approved.

The item

A description, unambiguous identification such as serial and asset number, and where relevant its condition on receipt.

Dates

Receipt where it is critical to validity, the date or dates of calibration, and the date of issue.

The results

With units of measurement, and a statement that they relate only to the item calibrated.

Deviations

Any additions to, deviations from or exclusions from the method.

Who authorised it

Identification of the person or persons authorising the certificate, who must be an authorised signatory with current competence for the method.

External results

Clear identification of any result that came from an external provider.

The one most often missing on real certificates is the quietest: the page footer. A certificate rendered without Page n of N and a stated end has no way of showing that a page is missing, which is what the clause is for.

What must a calibration certificate carry in addition?

ISO/IEC 17025 §7.8.4 adds, paraphrased:

Measurement uncertainty

Of the result, in the same unit as the result or relative to it, with the coverage factor and confidence.

Conditions

The environmental conditions under which the calibration was made where they influence the result: temperature, humidity.

Traceability

A statement of how the results are metrologically traceable, which in practice names the reference standard and its own certificate.

Before and after

Results before and after any adjustment or repair, if either was done.

Conformity

Where a statement of conformity is made, the specification, the results it applies to and the decision rule used.

Opinions

Any opinions and interpretations, clearly marked as such.

And one thing it must not carry: ISO/IEC 17025 §7.8.4.3. A due date printed by default is a recommendation the laboratory may have no basis for, because the right interval depends on how the customer uses the instrument. Where the customer has agreed an interval, it can be printed and the recall can be driven from it.

What is wrong with the certificates laboratories already issue?

These are the gaps found across eight years of one Australian laboratory's certificates when they were brought into this software. They are common because none of them makes a certificate look wrong.

• A pass with no decision rule. Every tolerance-band certificate stated pass or fail; not one declared the rule. The decision rules guide covers what the statement has to say.
• The uncertainty in the wrong unit. A jack calibrated in kN with ±U printed in the MPa the gauge reads. Every test checked the number; none checked the word after it.
• A master past its own due date. Nine certificates across six customers were issued against a reference standard whose calibration had lapsed, the worst by 455 days. ISO/IEC 17025 §6.4.6 and ISO/IEC 17025 §6.5 make that result untraceable, and §7.10 makes telling the customer the laboratory's decision.
• A signatory with no competence record. Authorisation under ISO/IEC 17025 §6.2.6 is per method, and a certificate signed by somebody not authorised for that method is the first thing an assessor tests.
• No footer, no page count. On every certificate rendered by a template that had positioned the footer off the page.

What does amendment require?

ISO/IEC 17025 §7.8.8. When an issued certificate has to change, the change is clearly identified, the reason is stated, and the amended certificate is uniquely identified and references the original. Nothing in the clause permits editing the original, and the original must be retained under ISO/IEC 17025 §8.4. In practice that means a certificate number stays the same, a revision moves on, and the first version is still readable by anybody who holds a copy of it.

It also means the old verification link has to keep working and start saying amended, because the person scanning last year's sticker on a torque wrench is exactly the person who needs to know.

Why does an issued certificate have to be immutable?

Because ISO/IEC 17025 §7.5 requires the laboratory to be able to reproduce the result, and a document that can be altered after issue cannot prove what the customer was told. The practical shape is: every number on the certificate is computed from stored raw readings by a versioned engine, the certificate is recomputed at the moment of issue and refused if it differs from the draft, the rendered file is written once to storage that does not permit overwriting, and its hash is recorded with the certificate. A reprint a year later produces the same bytes. That is what makes the hash a claim rather than a decoration.

Public verification follows from it. A random token printed as a QR code lets a stranger holding the instrument confirm that the certificate exists, is current, and has not been amended or withdrawn. Random rather than sequential matters: a sequential number lets anyone enumerate every certificate a laboratory has ever issued, which is a confidentiality breach under ISO/IEC 17025 §4.2. CalibraWorks issues certificates this way, and verification is never switched off, including for a laboratory that has stopped paying, because the person scanning the code never agreed to anything.