Last Updated on December 22, 2025 by Melissa Lazaro

Why an ISO/IEC 17043 Internal Audit Checklist Matters

If you’ve worked with ISO standards long enough, you start to notice patterns.

Here’s what I’ve noticed with ISO/IEC 17043 specifically:
most proficiency-testing (PT) providers know they need internal audits, but they’re not always sure what auditors actually expect to see.

I’ve supported PT providers at every stage. First-time accreditation. Surveillance audits. Even post-suspension recovery. And in almost every case, weak internal audits were part of the problem.

The intent behind this article is simple.

You’re here because you want:

• A clear ISO/IEC 17043 internal-audit checklist
• Confidence that you’re auditing the right things
• Fewer surprises during accreditation audits

By the end, you’ll know exactly what an effective internal audit looks like under ISO/IEC 17043—and how to use a checklist that actually protects you, not just ticks boxes.

What an ISO/IEC 17043 Internal Audit Checklist Must Cover

Internal audits under ISO/IEC 17043 aren’t just a formality. They’re one of the strongest indicators auditors use to judge how well your PT provider really operates.

This is important because accreditation bodies don’t just audit documents.
They audit how PT schemes are designed, run, evaluated, and improved.

A solid internal-audit checklist must cover:

• Impartiality and confidentiality
• Organizational structure and responsibilities
• Personnel competence, facilities, and equipment
• PT scheme design, operation, and statistical evaluation
• Management-system controls and improvement

Here’s a common mistake I see.

Many providers reuse an ISO/IEC 17025 internal audit checklist. On paper, it feels efficient. In practice, it misses critical PT-specific risks—especially around scheme design and performance evaluation.

Pro tip:
If your checklist doesn’t force you to audit how assigned values are determined or how performance criteria are justified, it’s incomplete.

ISO/IEC 17043 Clause-by-Clause Internal Audit Checklist Breakdown

Now that we’ve set the scope, let’s break it down properly.

An effective checklist should align clearly with Clauses 4 to 8 of ISO/IEC 17043. Not just as headings, but as auditable processes.

Here’s how that plays out in real audits:

• Clause 4 – Impartiality & Confidentiality
  Are risks identified, documented, and actively managed?
  Or is this just a policy that no one reviews?
• Clause 5 – Structural Requirements
  Do roles and responsibilities make sense in practice?
  Auditors often spot gaps between org charts and real operations.
• Clause 6 – Resource Requirements
  Are PT staff and statisticians competent for the schemes they run?
  Competence isn’t generic. It’s scheme-specific.
• Clause 7 – PT Scheme Design & Operation
  This is where most findings occur.
  Design rationale, homogeneity, stability, statistical methods—each needs evidence.
• Clause 8 – Management System
  Internal audits, corrective actions, and management reviews must actually connect.

Pro tip:
Turn each clause into open audit questions, not yes/no checks.
Auditors want to see thinking, not compliance theatre.

How to Use the ISO/IEC 17043 Internal Audit Checklist Effectively

A checklist alone doesn’t make an audit effective. How you use it matters just as much.

Here’s what works in practice.

Start with planning:

• Define the audit scope clearly
• Select auditors who understand PT activities
• Decide which PT schemes will be sampled

During the audit:

• Interview scheme coordinators and statisticians
• Observe processes where possible
• Trace records from design to reporting

One thing I always advise clients:
don’t audit everyone at once. Sample intelligently.

Common pitfall:
Auditing two days before the accreditation visit.
That turns internal audits into panic exercises instead of improvement tools.

In my experience, providers who audit early and follow up properly walk into accreditation audits far more relaxed—and it shows.

Common ISO/IEC 17043 Internal Audit Findings and How to Catch Them Early

After sitting through countless accreditation audits, certain findings come up again and again.

Here are some of the most common ones:

• Impartiality risks identified but never reviewed
• Statistical methods used without documented justification
• Weak traceability for assigned values
• Internal audits that don’t generate meaningful corrective actions

This is where a good checklist earns its keep.

The right questions force you to:

• Challenge assumptions
• Verify evidence
• Identify trends, not isolated issues

Pro tip:
Add a “why” column to your checklist.
If your team can’t explain why something is done a certain way, that’s a red flag worth exploring.

Downloadable ISO/IEC 17043 Internal Audit Checklist – What You’ll Get

The internal-audit checklist linked to this page was built from real accreditation experience—not theory.

Here’s what it includes:

• Clause-mapped audit questions aligned to ISO/IEC 17043
• Space to record objective evidence
• Sections for findings, observations, and nonconformities
• Guidance to help classify issues correctly

It’s designed to work whether you’re:

• Preparing for initial accreditation
• Managing surveillance audits
• Strengthening your management review inputs

If you’re a smaller PT provider, you can scale it easily.
The structure stays the same. The depth adjusts to your risk and scope.

FAQs – ISO/IEC 17043 Internal Audit Checklist

How often should ISO/IEC 17043 internal audits be performed?
At least annually, but more often if risks are high or major changes occur. Many providers audit different clauses at different times.

Can PT scheme staff conduct internal audits themselves?
They can, as long as independence is maintained. In practice, cross-auditing between schemes works well.

Can I use an ISO/IEC 17025 internal audit checklist instead?
Not on its own. ISO/IEC 17043 has unique requirements that must be audited separately.

Conclusion – Strengthen Your ISO/IEC 17043 Compliance with the Right Checklist

Internal audits are one of the clearest signals of maturity under ISO/IEC 17043.

When done properly, they:

• Reduce accreditation risks
• Improve PT scheme quality
• Build confidence across your team

I’ve seen providers transform their audit outcomes simply by asking better questions and using a checklist built for PT realities.

If you want fewer surprises and stronger audit results, start there.

Next step:
Download the ISO/IEC 17043 internal-audit checklist and use it as a real improvement tool—not just a compliance exercise.