What is an auditor's expert?
ISA 620.7 requires the auditor to determine whether to use an expert when expertise in a field other than accounting or auditing is needed to obtain sufficient appropriate audit evidence. Common examples include property valuers, actuaries, environmental scientists, and IT security specialists.
ISA 620.5 is clear: the auditor retains sole responsibility for the audit opinion. Using an expert does not transfer or dilute that responsibility. The expert provides evidence. The auditor evaluates it.
Before engaging an expert, ISA 620.9 requires the auditor to evaluate three things: competence (does the expert hold relevant qualifications and have relevant experience?), capability (can the expert complete this specific engagement within the required timeframe?), and objectivity (do any relationships or circumstances create threats to the expert's objectivity?). ISA 620.11 requires the scope, nature, and objectives of the work to be agreed in writing.
Key Points
- The auditor retains full responsibility for the audit opinion, even when relying on an expert's work.
- ISA 620.9 requires evaluating the expert's competence, capabilities, and objectivity before using their work.
- The agreement must be documented, ideally in writing per ISA 620.11.
- An auditor's expert is not the same as a management's expert — different ISAs govern each.
Why it matters in practice
The FRC found audit files where the auditor engaged an expert but did not evaluate objectivity. Competence was assessed (the expert had the right qualifications), but the file contained no consideration of whether relationships between the expert and the client, or the expert and the firm, created threats. ISA 620.9 requires all three elements.
A second recurring finding: teams treat the expert's report as audit evidence without evaluating the methodology. Receiving a well-formatted report from a qualified specialist is not sufficient. ISA 620.12(a) requires the auditor to evaluate the relevance and reasonableness of the expert's findings, including the assumptions used, the methods applied, and whether the conclusions are consistent with other audit evidence.
Worked example: Navarro Logística S.L.
Client: Spanish logistics company, FY2024, revenue €62M, IFRS reporter. Four warehouse properties carried at fair value under IAS 40.33, total €23.5M (38% of total assets).
Management's valuer: Pérez Tasaciones S.L. values the portfolio at €24.8M using a capitalisation rate of 5.9% based on two comparable transactions.
Auditor's expert: The engagement team engages Montero & Asociados, a RICS-accredited valuation firm with no prior relationship with the client. Montero uses four comparable transactions and arrives at a capitalisation rate of 6.8%, producing a range of €22.1M–€24.0M.
Evaluation: Management's €24.8M exceeds the top of the auditor's expert's range. The key difference is the capitalisation rate: 5.9% vs 6.8%, driven by the number and quality of comparables. The auditor evaluates Montero's methodology (four comparables with full data vs Pérez's two) and concludes the auditor's expert's range is more supportable.
Resolution: Management adjusts to €24.0M (the top of Montero's range). No misstatement remains.
Auditor's expert vs management's expert
| Dimension | Auditor's expert | Management's expert |
|---|---|---|
| Who engages | The auditor | Management |
| Governing ISA | ISA 620 | ISA 500.8 |
| Purpose | Help auditor obtain evidence | Help management prepare statements |
| Responsibility | Auditor evaluates, retains opinion responsibility | Management responsible for resulting figures |
| Objectivity evaluation | Required under ISA 620.9 | Required under ISA 500.8 |
Key standard references
- ISA 620.6(a): Defines auditor's expert.
- ISA 620.5: Auditor retains sole responsibility for the opinion.
- ISA 620.7: Auditor determines whether to use an expert.
- ISA 620.9: Evaluate competence, capability, and objectivity.
- ISA 620.11: Agree scope and terms in writing.
- ISA 620.12: Evaluate adequacy of the expert's work.
Related terms
Related reading
Frequently asked questions
Does using an auditor's expert reduce the auditor's responsibility for the opinion?
No. ISA 620.5 is unambiguous: the auditor retains sole responsibility for the audit opinion, and that responsibility is not reduced by the auditor's use of an expert.
What must the auditor evaluate about an auditor's expert?
ISA 620.9 requires evaluating competence (relevant qualifications and experience), capability (can they do this specific job in this timeframe), and objectivity (do any relationships compromise independence).