ISO/IEC 17025 for testing and calibration laboratories: what UKAS assessors focus on

Laboratory technician recording calibration readings on a tablet

Most of my work is with ISO management systems, where a business is certified. (If you’re still working out which ISO standard you actually need, start there.) Laboratories are different. In the UK, a testing or calibration laboratory working to ISO/IEC 17025 is accredited by UKAS, and that difference shapes the whole process, from what the assessors look at to who they send.

This guide explains what ISO/IEC 17025 is, why it’s accreditation and not certification, how the UKAS process runs, and the areas where laboratories most often need to tighten up before assessment.

What ISO/IEC 17025 is

The current version is ISO/IEC 17025:2017, General requirements for the competence of testing and calibration laboratories. It’s the third edition, published in November 2017, and it replaced the 2005 edition.

ISO describes it as “the international standard for testing and calibration laboratories” and says it “sets out requirements for the competence, impartiality, and consistent operation of laboratories.” The IEC’s listing adds that it “is applicable to all organizations performing laboratory activities, regardless of the number of personnel.” So a two-person calibration business and a large testing house are working to the same standard.

When it was published, ISO said the 2017 edition covered “technical changes, vocabulary and developments in IT techniques” and that it “takes into consideration the latest version of ISO 9001” (at that time, ISO 9001:2015).

Is a new edition on the way?

I checked this because people keep asking. As of October 2026, ISO lists ISO/IEC 17025:2017 as published and current. Its page states the standard “was last reviewed and confirmed in 2023”, and there’s no revision shown as under development. ISO reviews standards every five years, so it’s worth checking the ISO page from time to time, but for now 2017 is the edition you work to.

Accreditation and certification are not the same thing

This is the point I’d most like every lab manager to be clear on, because it changes how you prepare.

UKAS explains that certification “is an audit of whether an organisation, product or individual, conforms to the criteria” of a standard or scheme. ISO 9001 is the classic example. Accreditation goes further: it “involves the assessment of the competence and impartiality of an organisation.” UKAS describes accreditation as “a rung further up the ladder.”

For a laboratory, that means the assessor isn’t only checking that you have a documented system. They’re checking whether you are technically competent to produce valid results for the specific tests or calibrations you offer. Accreditation is also tied to scope. As BSI puts it, a laboratory “may only hold accreditation in relation to a particular type of testing”, and its schedule of accreditation “will confirm the exact scope.”

In the UK, UKAS describes itself as “the only organisation recognised by Government to accredit calibration activities” against ISO/IEC 17025. So:

UKAS assesses and accredits your laboratory
a consultant like me helps you prepare, but cannot accredit you
you’re “UKAS accredited” for the scope on your schedule, not “ISO 17025 certified”
holding ISO 9001 certification is not the same as being accredited to ISO/IEC 17025

That third bullet is worth getting right in your marketing, tender responses, and website copy. Assessors notice.

How the UKAS process works

UKAS sets out its process on its gain accreditation page and in its publication GEN 1 (Edition 4, March 2025). In summary:

Carry out a gap analysis against the standard and the relevant UKAS publications.
Apply to UKAS and pay the application fee. You’re then assigned an Assessment Manager.
Optionally, have a pre-assessment. UKAS says it is optional but “can be a valuable step”, and GEN 1 strongly recommends it for organisations with little or no accreditation experience.
Initial assessment, which covers records, interviews, witnessed activities, and a full audit.
Clear any findings. UKAS says you’ll have approximately 12 weeks after an initial assessment, and GEN 1 allows up to three months.
An independent UKAS decision-maker ratifies the grant of accreditation.

After that, the first surveillance visit takes place six months after the grant, then surveillance is annual, with a full reassessment every fourth year.

One difference from certification audits is how findings are graded. GEN 1 uses “M” for action that is mandatory (a nonconformity that must be resolved) and “R” for action that is recommended. For surveillance and reassessment visits, GEN 1 says the time allowed to clear findings is generally one month, which is much tighter than many labs expect.

What UKAS assessors focus on

Because accreditation is about competence to produce valid results, the assessment goes much deeper into the technical work than a typical ISO 9001 audit. These are the areas I’d make sure are solid.

Witnessed work

GEN 1 says an initial assessment normally includes witnessing of the activities, preferably live. Expect an assessor to watch staff carry out tests or calibrations and compare what they do with your documented method.

Metrological traceability

Your results need to trace back to recognised measurement standards. UKAS policy TPS 41 sets out acceptable sources, including national measurement institutes covered by the CIPM MRA for those services, and calibration laboratories accredited for those services by an accreditation body within the ILAC Arrangement. A common gap I see is a calibration certificate on file that doesn’t actually cover the range or parameter the lab relies on.

Measurement uncertainty

UKAS publishes M3003, The expression of uncertainty and confidence in measurement, to support policy on evaluating and reporting uncertainty for testing and calibration laboratories. Assessors will want to see uncertainty budgets that match your current methods and equipment, not ones written years ago for a setup you no longer use.

Proficiency testing and checks on validity

UKAS policy TPS 47 (Edition 5, January 2023) states that “all accredited laboratories shall participate in PT/ILCs where such schemes are available and relevant.” Labs must also document a plan for the level and frequency of participation, justify any non-participation, and monitor their performance over time. UKAS issued a draft Edition 6 for consultation in May 2026, so check the UKAS publications list for the version in force when you prepare.

Competence and impartiality

ISO puts competence and impartiality at the heart of the standard. In my experience, assessors look for evidence that each person is authorised for the specific activities they perform, and that nothing (commercial targets or customer pressure, for example) is allowed to influence results. Training records that show attendance but not demonstrated competence are a frequent weak spot.

The management system side

Accredited labs still need internal audits, management review, complaints handling, and corrective action. The difference is that these must cover the technical work too. An internal audit that only checks document control will not satisfy an assessor. My articles on management review and the top 10 nonconformities we see in SMEs apply just as much to laboratories.

FAQs

What is the current version of ISO/IEC 17025?

The current version is ISO/IEC 17025:2017, the third edition, published in November 2017. ISO states it was last reviewed and confirmed in 2023 and remains current, with no revision shown as under development as of October 2026.

Is ISO/IEC 17025 accreditation or certification?

Accreditation. In the UK, laboratories are accredited to ISO/IEC 17025 by UKAS. Accreditation assesses technical competence and impartiality for a defined scope, which goes further than certification to a management system standard such as ISO 9001.

How often does UKAS assess an accredited laboratory?

UKAS carries out the first surveillance visit six months after accreditation is granted, then annual surveillance, with a full reassessment every fourth year.

How long do I have to clear UKAS findings?

UKAS GEN 1 allows up to three months to clear findings after an initial assessment or an extension to scope. After surveillance and reassessment visits, the time allowed is generally one month.

Is proficiency testing mandatory for UKAS accredited labs?

UKAS policy TPS 47 states that all accredited laboratories shall participate in proficiency testing or interlaboratory comparisons where such schemes are available and relevant, following a documented participation plan.

Can a consultant accredit my laboratory?

No. Only UKAS can grant UKAS accreditation. A consultant can help you prepare your system, run a gap analysis, and carry out internal audits before assessment.

Get ready for your UKAS assessment

If you’re preparing for initial accreditation, extending your scope, or recovering from a difficult assessment, I can help you get your quality system and records into shape. To be clear about roles: CAW Consultancy helps laboratories prepare, and UKAS carries out the assessment and grants accreditation. We offer a free gap analysis to start.

Call 01257 824481, email Craig@cawconsultancy.co.uk, or visit www.cawconsultancy.co.uk.

If paper records are slowing your lab down, CAW Digital builds bespoke paperless management systems, and Compliance Master can help you keep track of actions, audits, and reviews in one place.

Sources

Craig Willetts is the founder of CAW Consultancy Business Solutions Ltd and a UK lead auditor with over 20 years’ experience across ISO management systems and UK security industry schemes.