Can an external auditor perform an internal audit in the UK?

In the UK, it is generally not recommended for an external auditor to perform internal audit functions for the same organization due to concerns about independence and conflicts of interest.

Why are the two roles kept separate?

External auditors

External auditors are responsible for providing an independent opinion on whether a company's financial statements present a true and fair view in accordance with applicable accounting standards and legal requirements. To maintain credibility, they must remain objective and independent from the organization they audit.

Internal auditors

Internal auditors evaluate and improve an organization's:

• Internal controls
• Risk management processes
• Governance framework
• Operational efficiency

Because internal auditors work closely with management and may advise on improving business processes, their role is fundamentally different from that of an external auditor.

Independence and conflict of interest

If the same audit firm performs both external and internal audit services for the same client, it may create self-review threats and other conflicts of interest. For example, an external auditor could be placed in the position of evaluating controls or processes that their own firm helped design or assess during the internal audit.

To protect auditor independence, UK professional and ethical standards generally discourage this arrangement and require firms to identify and manage any threats to independence before accepting non-audit services.

UK professional standards

Professional bodies such as:

• The Institute of Chartered Accountants in England and Wales (ICAEW)
• The Association of Chartered Certified Accountants (ACCA)

emphasize the importance of maintaining auditor independence. In addition, ethical standards applicable in the UK require external auditors to avoid engagements that could compromise, or appear to compromise, their objectivity.

Conclusion

While there may be limited circumstances where an external audit firm can provide certain internal audit services, provided appropriate ethical safeguards are in place and independence is not impaired, it is generally discouraged for an external auditor to perform the internal audit of the same organization. Keeping these functions separate helps preserve auditor independence, reduces conflicts of interest, and strengthens confidence in the organization's financial reporting and governance.