Verify a Supplier's ISO 17025 Accreditation

An ISO/IEC 17025 accreditation claim from a calibration or testing supplier is not a single yes/no fact — it is a specific, dated, scope-limited assertion made by a specific accreditation body about a specific site performing specific test or calibration methods. Procurement and lab-management teams that treat “ISO 17025 accredited” as a checkbox on a vendor questionnaire routinely end up contracting work that the supplier’s accreditation never actually covered. This guide walks through how to verify an ISO/IEC 17025 accreditation claim before you sign, not just what the standard says in the abstract.

For a full explanation of what ISO/IEC 17025 accredits and how it differs from ISO 9001 certification, see CASRAI’s ISO/IEC 17025 guide. This page assumes that background and focuses on the procurement-side verification task.

Why an “ISO 17025 accredited” claim needs verification, not just acceptance

Unlike ISO 9001, which certifies a management system in general, ISO/IEC 17025 accreditation is granted method-by-method and site-by-site. An ISO 17025 accredited laboratory is not accredited for “testing” or “calibration” in general — it is accredited for a defined list of test methods, measurement parameters, ranges, and associated uncertainties, published in a document usually called the scope of accreditation. A lab can be genuinely, validly accredited to ISO/IEC 17025 and still be performing the specific test or calibration you need entirely outside that scope. That is the single most common gap procurement teams miss, and it is the reason a supplier’s accreditation status can’t be verified from a logo on a quote or a line in a capabilities statement.

Who accredits laboratories to ISO/IEC 17025

ISO/IEC 17025 accreditation is issued by a national or regional accreditation body, not by ISO itself (ISO writes the standard; it does not accredit anyone). In the United States, the accreditation bodies that most commonly appear on calibration and testing lab certificates are:

A2LA — American Association for Laboratory Accreditation
ANAB — ANSI National Accreditation Board
NVLAP — National Voluntary Laboratory Accreditation Program, operated by NIST (used for specific, defined test categories rather than general-purpose accreditation)
PJLA — Perry Johnson Laboratory Accreditation

Internationally, the accreditation body that issued a given certificate is normally a signatory to the ILAC (International Laboratory Accreditation Cooperation) Mutual Recognition Arrangement (ILAC MRA). ILAC MRA membership is what allows a test or calibration report from an accredited lab in one country to be accepted in another without re-testing. If a supplier cites an accreditation body you don’t recognize, checking whether that body is an ILAC MRA signatory is a reasonable first filter — but it does not replace checking the supplier’s own certificate and scope directly.

How to verify a supplier’s ISO/IEC 17025 accreditation: a step-by-step check

1. Get the exact legal entity name, site address, and certificate number

Ask the supplier directly for these three things rather than relying on a marketing page. Accreditation attaches to a specific legal entity operating at a specific address — a parent company’s accreditation does not automatically extend to every branch, subsidiary, or newly opened site.

2. Identify the accreditation body and look the certificate up directly

Every major accreditation body maintains a public, searchable directory of currently accredited laboratories — this is the primary way to confirm a claim independent of anything the supplier tells you. Search the directory by the supplier’s legal entity name or certificate number rather than trusting a PDF the supplier provides, since a scanned certificate can be outdated, altered, or belong to a different site of the same company.

3. Confirm the scope of accreditation actually covers what you’re buying

This is the step most procurement teams skip, and it’s the one that matters most. Open the published scope of accreditation (the accreditation body’s directory listing typically links to it, or the supplier can provide it directly) and confirm it lists:

The exact test method or calibration parameter you need (e.g., a specific ASTM/USP method, or a specific measurement quantity such as mass, temperature, or pressure)
The measurement range you need covered
For calibration: the Calibration and Measurement Capability (CMC) — the best uncertainty the lab is accredited to achieve at that range — is tight enough for your application

If your specific method or range isn’t listed, the work is being performed outside the lab’s accreditation, even if the lab is genuinely accredited for other things. A report generated for out-of-scope work should not carry the accreditation body’s symbol or claim ISO/IEC 17025 accredited status for that specific result.

4. Check the certificate’s validity dates

Accreditation is issued for a fixed cycle (commonly reassessed every 1-2 years depending on the accreditation body, with ongoing surveillance in between) and can be suspended, restricted, or withdrawn between full reassessments. A directory listing showing “active” status as of your check date is more reliable than a certificate date printed on a document that could be a year or more old.

5. Match the accredited site to the site actually doing your work

If a supplier operates multiple labs, confirm the accreditation you verified belongs to the site that will physically perform your test or calibration — not a different, accredited sister site used only in the sales conversation.

What to request in the supplier qualification file

For a documented, auditable procurement record, request and retain:

The current accreditation certificate, including certificate number and accreditation body
The current scope of accreditation document (not a summary — the actual scope listing)
A statement of the specific site/address the work will be performed at
Confirmation of the next scheduled reassessment or surveillance date, if the supplier will share it
A commitment to notify you of any suspension, restriction, or withdrawal of accreditation during the contract term

This file is also what a customer audit or regulatory inspection will ask for later — building it at qualification time, rather than reconstructing it after the fact, is significantly less work. See CASRAI’s guide to the vendor qualification process for how this fits into a broader supplier-approval workflow, and calibration certificates and metrological traceability for what a compliant calibration report itself needs to show once you’ve confirmed the supplier is properly accredited.

Common red flags and claim problems

“ISO 17025 compliant” instead of “ISO 17025 accredited.” These are not the same claim. “Compliant” or “meets the requirements of” is a self-declared claim with no independent verification behind it. “Accredited” means an accreditation body has formally assessed and attested to it. Treat the two phrases as materially different and ask which one is actually true.
ISO 9001 certification presented as equivalent. ISO 9001 certifies a general quality management system; it does not assess technical competence to perform specific test or calibration methods the way ISO/IEC 17025 does. A supplier that is ISO 9001 certified but not ISO/IEC 17025 accredited has not had its technical results independently verified.
Accreditation body logo used without a checkable certificate number. A logo alone is not evidence; ask for the number and check the directory.
Scope creep over the life of the contract. A supplier accredited for your work at the time of qualification can lose or narrow that scope later. Re-verification at renewal, not just at initial qualification, is what a maintenance clause in the contract is for.

Building accreditation verification into contracts and purchase orders

Once verification is done, the finding should be reflected in the contract or PO terms, not just kept in a qualification file that nobody re-checks. Common clauses include: a requirement that the supplier maintain active ISO/IEC 17025 accreditation covering the specific scope of work for the contract term; a notification obligation if accreditation is suspended, restricted, or withdrawn; and a right to request current scope documentation on demand. This converts a one-time verification check into an ongoing contractual obligation, which matters because accreditation status can change mid-contract in a way a single qualification-stage check can’t catch.

Illustrative example: a scope gap on a calibration supplier

This is an illustrative composite, not a real named lab or case, included to show how the scope check applies in practice. A lab procurement team qualifies a calibration supplier that is genuinely ISO/IEC 17025 accredited, verified against the accreditation body’s public directory. The team assumes this covers all calibration work sent to the supplier. Months later, an internal audit finds that a batch of pressure-gauge calibrations was sent to the same supplier — but the supplier’s published scope of accreditation only covers temperature and mass calibration, not pressure. The pressure calibration certificates were valid documents from a real, accredited lab, but the specific measurement quantity was outside that lab’s accredited scope, so the certificates could not be relied on as ISO/IEC 17025-accredited results for that parameter. The fix was procedural: matching the accredited scope to the specific purchase order line item, not just to the supplier as a whole, before each order is placed.

Frequently asked questions

Is ISO/IEC 17025 accreditation mandatory for a calibration or testing supplier?

Not universally by law, but it is frequently required by customer contracts, regulatory frameworks, or a buyer’s own quality system (for example, a lab operating under ISO/IEC 17025 itself is generally required to use accredited external calibration providers wherever accredited services are available, per ISO/IEC 17025:2017 Clause 6 on externally provided products and services). Whether it’s mandatory in your case depends on your own regulatory and contractual obligations, not on a blanket rule.

What is the difference between an ISO 17025 accredited laboratory and one that is just “ISO 17025 compliant”?

Accredited means an independent accreditation body has formally assessed the lab against the standard and issued a certificate with a defined scope. Compliant (or “meets the requirements of”) is a self-declared claim with no independent assessment behind it. Only the accredited claim can be checked against a public directory.

How do I check if a lab’s ISO/IEC 17025 accreditation is currently valid?

Search the issuing accreditation body’s public directory by the lab’s legal entity name or certificate number and confirm the listing shows active status and a scope of accreditation that covers the specific method or parameter you need — not just the certificate date printed on a document the supplier provided.

Does ISO 9001 certification substitute for ISO/IEC 17025 accreditation?

No. ISO 9001 certifies a general quality management system. ISO/IEC 17025 accreditation additionally assesses technical competence for specific test and calibration methods. A supplier can hold one without the other, and a buyer needing verified technical results specifically needs the ISO/IEC 17025 accreditation, not ISO 9001 alone.

Who accredits laboratories to ISO/IEC 17025 in the United States?

The most commonly seen accreditation bodies for US calibration and testing labs are A2LA, ANAB, NVLAP (operated by NIST for specific test categories), and PJLA. Each maintains its own public directory of currently accredited labs and their scopes.

ISO/IEC 17025 Accreditation: How to Verify a Supplier Before You Sign

Ask about ISO/IEC 17025 Accreditation: How to Verify a Supplier Before You Sign