Advanced Audit and Assurance (International) · Using the work of others

Using the Work of an Auditor's Expert (ISA 620)

Updated 11 October 2026 · Fact-checked

ISA 620 covers an expert in a field other than accounting or auditing whose work the auditor uses as evidence. You decide if one is needed, assess their competence, capabilities and objectivity, agree the scope in writing, then evaluate whether their work is adequate. The auditor keeps sole responsibility for the opinion.

Understand Using the Work of an Auditor's Expert (ISA 620)

Some audit areas need skills you do not have as an auditor. Examples are valuing a property, estimating oil reserves, or measuring a pension liability. In these cases you may use an auditor's expert: an individual or organisation with expertise in a field other than accounting or auditing, whose work you use to obtain sufficient appropriate audit evidence. The expert can be internal to your firm or external.

The key point is responsibility. Using an expert does not reduce your responsibility for the audit opinion. The auditor's report should not refer to the expert unless law requires it, or unless the report is modified because of the expert's work. If you do refer to the expert, the report must say the reference does not reduce your responsibility.

Do not confuse the two types of expert. A management's expert is engaged by the entity to help it prepare the financial statements, for example the actuary who calculates the pension obligation. An auditor's expert is engaged by you. ISA 620 applies only to the auditor's expert. When management uses an expert, you treat their work as part of the evidence on the estimate and deal with it under ISA 500 and ISA 540. You may then still decide to engage your own expert to challenge it.

The standard follows a logical sequence. First, decide whether you need an expert, based on the risk of material misstatement and your own skills. Second, evaluate the expert: competence (qualifications, experience), capabilities (time, resources, ability to do the work) and objectivity (threats such as self-interest, familiarity or intimidation). Third, agree in writing the nature, scope and objectives of the work, each party's roles, communication, and confidentiality. Fourth, evaluate whether the work is adequate for your purposes.

If an expert is not objective, you do not automatically reject them. You assess the threats and the safeguards available. An expert employed by your own firm is usually subject to the firm's quality management and ethics policies, but an external expert may be more independent from the client. Either way, you must reach a conclusion and document it.

Key rules to remember

Definition of an auditor's expert: Auditor's expert = individual or organisation with expertise outside accounting and auditing, whose work the auditor uses as audit evidence; Can be internal or external to the audit firm. Engaged by the auditor, not by management.
Evaluation of the expert: Competence + Capabilities + Objectivity; Competence is about qualifications and experience. Capabilities is about time, resources and ability. Objectivity is about threats to bias and conflicts of interest.
Agreed matters in writing: Nature, scope and objectives of work; roles and responsibilities; nature, timing and extent of communication; confidentiality; Written agreement is the safest form. It avoids disputes about what the expert was asked to do.
Evaluating adequacy of work: Relevance and reasonableness of findings + assumptions and methods + source data; Check consistency with other audit evidence and whether the work addresses the assertion you are testing.
Responsibility rule: Auditor's responsibility for the opinion is not reduced by using an expert; Do not refer to the expert in an unmodified report, unless required by law or regulation.

How to solve Using the Work of an Auditor's Expert (ISA 620) questions

Use this sequence for any ISA 620 requirement. Tie each point to the scenario's facts, not to the standard in general.

1Identify the area and why expertise is needed: the risk of material misstatement, the complexity and the size of the balance.
2Decide whether the expert is the auditor's or management's. This sets which procedures apply.
3Evaluate competence: professional qualification, membership of a professional body, experience with this type of asset or location.
4Evaluate capabilities: time, resources, and whether the expert can do the work to your timetable.
5Evaluate objectivity: look for family, financial, or business ties with the client, and for fee dependence or pressure. State the threat and a safeguard.
6Agree the scope in writing: objectives, work to be done, access to data, communication, confidentiality, and reporting format.
7Evaluate the work: assess the source data, assumptions and methods, and compare the findings with other evidence. Follow up if inadequate.
8Conclude and document, and consider the effect on the audit report only if the expert's work leads to modification.

Quickest way: The C-C-O-S-E checklist

When to use it: Use it when a question says a specialist, valuer or actuary is involved and asks what the auditor should do. It also works for a 4-6 mark requirement.

C: Competence. Qualifications and experience relevant to the asset.
C: Capabilities. Time, resources and access to do the work.
O: Objectivity. Threats such as links to the client, and safeguards.
S: Scope. Agree the objectives, work and communication in writing.
E: Evaluate. Check data, assumptions, methods and consistency with other evidence.
Add one scenario-specific comment for each letter to earn application marks.

Common mistakes in Using the Work of an Auditor's Expert (ISA 620)

Applying ISA 620 to an expert engaged by management.
Students see the word expert and assume ISA 620 applies.
Fix: Check who engaged the expert. If management did, treat the work as evidence on an estimate and evaluate it under ISA 500 and ISA 540.
Saying the auditor can transfer responsibility to the expert.
It sounds logical that a specialist takes on the risk.
Fix: State clearly that the auditor remains solely responsible for the opinion, whatever the expert concludes.
Listing competence, capabilities and objectivity without applying them.
Students recall the headings but do not read the scenario.
Fix: Link each to a fact, for example the valuer's lack of experience in the region, or a family tie to the finance director.
Rejecting an expert as soon as a threat to objectivity appears.
Students treat any threat as disqualifying.
Fix: Evaluate the significance of the threat and the safeguards. Decide whether the threat can be reduced to an acceptable level, otherwise use another expert.
Ignoring the evaluation of the expert's work.
Students stop once the expert is appointed.
Fix: Add a step covering source data, assumptions, methods, and consistency with other evidence. If the work is inadequate, agree further work or perform other procedures.
Referring to the expert in the audit report as a matter of course.
Students think disclosure shows transparency.
Fix: State that an unmodified report does not refer to the expert. A reference is made only where required by law or where a modification is needed and the reference is relevant to understanding it.

Worked examples

Example 1

You are the audit senior on Zenith Retail, which holds freehold properties at a carrying amount of $48 million, being 40% of total assets, at revalued amounts. The valuation was prepared by Hale & Co, a firm of chartered surveyors engaged by Zenith. Your manager asks whether you can rely on it without further work. Explain the auditor's considerations. (6 marks)

Show the solution

Identify the type of expert. Hale & Co was engaged by management, so this is a management's expert and ISA 620 does not directly apply.
Explain the effect. The valuation is evidence on an accounting estimate and you must evaluate it under ISA 500 and ISA 540. You cannot just rely on it.
Evaluate competence and capabilities: check membership of a recognised professional body and experience with this type of property and location.
Evaluate objectivity: check for fee arrangements dependent on the value or any link to directors. These could be self-interest or familiarity threats.
Evaluate the work: obtain an understanding of methods, assumptions and source data, such as rental yields, floor areas and market comparables, and test these.
Consider whether you need your own expert. With 40% of total assets at stake, if you lack the expertise to challenge the valuation, engage an auditor's expert, which brings ISA 620 into play.

Answer: You cannot rely on the valuation without further work. Hale & Co is management's expert, so evaluate its competence, capabilities and objectivity, and test its data, methods and assumptions under ISA 500 and ISA 540. Because the properties are 40% of total assets, consider engaging your own auditor's expert under ISA 620 to challenge the valuation.

Example 2

Your firm has engaged Marlow Actuaries to assess the pension obligation of Brightwell Ltd, as the audit team lacks the skills. The lead actuary is the brother of Brightwell's finance director. Discuss how you will deal with the objectivity issue and what you will agree with the expert before work begins. (8 marks)

Show the solution

Identify the threat. The family tie creates a familiarity threat to objectivity, and there may also be an intimidation threat if the finance director can influence the actuary.
Assess significance. A close family relationship with a key client officer is a serious threat, since the finance director has influence over the balance being audited.
Consider safeguards. Ask Marlow to assign a different actuary who has no connection, or apply review by a second partner. If the threat cannot be reduced to an acceptable level, engage a different expert.
Document the evaluation and the conclusion reached.
Agree in writing: the objectives and scope of the work, such as the valuation date and assumptions to be reviewed.
Agree roles and responsibilities, including who is to test the data and what access is allowed.
Agree communication, including timing of reports and a requirement to raise issues promptly, and agree confidentiality of client information.
Later, evaluate the adequacy of the work: relevance and reasonableness of findings, assumptions, methods and source data.

Answer: The family tie is a significant familiarity threat. Replace the lead actuary with someone unconnected, or use another firm if safeguards are not enough. Before work starts, agree in writing the scope and objectives, roles, communication and confidentiality. After the work, assess its assumptions, methods and data, and consistency with other evidence.

Exam tips

Start every answer by deciding whether the expert is the auditor's or management's. It shows you can apply the standard and sets up the right procedures.
Apply competence, capabilities and objectivity to named facts in the scenario. Generic lists earn few marks.
For objectivity, always name the threat and a safeguard. Do not stop at identifying the problem.
For professional skills marks, show scepticism: challenge the valuation's assumptions and say what you would do if the evidence is inadequate.
Remember that responsibility stays with the auditor. A short sentence to this effect often earns a mark.

Practice questions from Using the work of others

Using the Work of an Auditor's Expert (ISA 620) in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Using the Work of an Auditor's Expert (ISA 620): frequently asked questions

What is the difference between an auditor's expert and a management's expert?

An auditor's expert is engaged by the auditor to help obtain audit evidence, and ISA 620 applies. A management's expert is engaged by the entity to help prepare the financial statements. Their work is audit evidence that you evaluate under ISA 500 and ISA 540.

How do I evaluate the competence and objectivity of an auditor's expert?

Competence covers qualifications, professional body membership and relevant experience. Capabilities cover time and resources. For objectivity, look for family, financial or business links, and consider safeguards. Document your conclusion.

Can the auditor refer to the expert in the audit report?

Not in an unmodified report, unless law or regulation requires it. Where a modified opinion is issued and the reference helps users understand it, the report may refer to the expert but must state that the reference does not reduce the auditor's responsibility.

What should I do if the expert's work is not adequate?

Agree with the expert any additional work needed. If that cannot resolve the issue, perform other appropriate procedures. If you still lack sufficient appropriate evidence, consider the effect on the audit opinion.