The International Standards on Auditing (UK), or ISAs (UK), are the international auditing standards issued by the IAASB with extra UK requirements and guidance added by the Financial Reporting Council. The UK additions are shaded grey in the FRC’s texts and new UK paragraphs are numbered as suffixes to the international paragraph they follow, so you can see at a glance what is international and what is local. The standards are numbered in series from 200 to 805, running from general principles through risk assessment, evidence and the work of others to the auditor’s report.

Who sets the ISAs (UK) and why do they apply?

The FRC has been designated as the competent authority for audit in the UK by the Statutory Auditors and Third Country Auditors Regulations 2016 (SI 2016/649). That gives it the authority to determine the technical standards for statutory audits under the Companies Act 2006. The FRC’s Scope and Authority of Audit and Assurance Pronouncements (March 2023) explains that the ISAs (UK), together with the FRC’s Ethical Standard, apply to:

  • statutory audits of companies under the Companies Act 2006;
  • audits required by other UK legislation, such as those of building societies, credit unions, friendly societies, pension funds, charities and registered social landlords;
  • public sector audits, because the national audit agencies have chosen to adopt the FRC’s standards; and
  • other audits by firms registered with the UK members of the CCAB (ICAEW, ICAS, ACCA and CIPFA), unless the engagement requires other recognised standards.

An auditor who fails to follow the standards is liable to investigation by the FRC or by its professional body, and the sanctions can include withdrawal of registration and with it eligibility to carry out company audits. For who can sign audits, see who can act as a registered auditor.

How are the international standards adapted for the UK?

The FRC starts from the IAASB text and, where necessary, adds requirements and application material suited to UK law, culture and business practice. Three features identify the UK material:

  • Grey shading. Paragraph 18 of the Scope and Authority document says the additional material is clearly differentiated from the international text by grey shading.
  • Suffix numbering. New UK paragraphs are slotted in after the international paragraph they relate to and carry its number plus a suffix. For example, ISA (UK) 230 adds a UK paragraph after paragraph 8 (retain other data and documents important in supporting the auditor’s report) and another after paragraph 14 (retain documentation important for monitoring compliance). ISA (UK) 200 adds one after application paragraph A17, explaining that UK auditors have ethical requirements from two sources: the FRC’s Ethical Standard and their own professional body.
  • “In the UK” wording. Some additions sit inside an existing paragraph. ISA (UK) 230 paragraph 14, for instance, says that in the UK the final audit file must be assembled no later than 60 days after the date of the auditor’s report.

The FRC states that the ISAs (UK) do not conflict with the IAASB’s ISAs, so an audit carried out under the ISAs (UK) can also be described as complying with the international standards. The reverse is not true: an audit under the IAASB text alone would miss the UK additions.

How are the standards organised?

The FRC publishes the full list on its auditing standards page. Grouped by number, the series runs roughly as follows.

Series Subject Examples
200 to 299 General principles and responsibilities 200 overall objectives; 210 terms of engagement; 220 quality management for an audit; 230 documentation; 240 fraud; 250 laws and regulations; 260 and 265 communication with those charged with governance
300 to 499 Risk assessment and response 300 planning; 315 identifying and assessing risks; 320 materiality; 330 responses to assessed risks; 402 service organisations; 450 evaluating misstatements
500 to 599 Audit evidence 500 audit evidence; 505 external confirmations; 530 sampling; 540 accounting estimates; 550 related parties; 560 subsequent events; 570 going concern; 580 written representations
600 to 699 Using the work of others 600 group audits; 610 internal auditors; 620 auditor’s experts
700 to 799 Conclusions and reporting 700 forming an opinion; 701 key audit matter reporting; 705 modified opinions; 706 emphasis of matter and other matter paragraphs; 710 comparatives; 720 other information
800 to 899 Specialised areas 800 special purpose frameworks; 805 single statements and specific elements

Sitting above the engagement standards are the firm level standards, ISQM (UK) 1 on quality management and ISQM (UK) 2 on engagement quality reviews, and the FRC’s Ethical Standard. Our guides to ISQM (UK) 1 and the Ethical Standard cover those.

What is inside each standard?

ISA (UK) 200 explains the anatomy. Each standard contains:

  1. Introduction: scope, subject matter, responsibilities and an effective date.
  2. Objective: what the auditor is trying to achieve in that area.
  3. Definitions, where needed.
  4. Requirements, expressed with the word “shall”.
  5. Application and other explanatory material, the “A” paragraphs, which explain what a requirement means and give examples. They do not impose requirements on their own, but paragraph 19 of ISA (UK) 200 requires the auditor to understand the entire text, including this material.

Some standards also include considerations for smaller and less complex entities and for the public sector. Paragraph A68 of ISA (UK) 200 is clear that these help apply the requirements but do not reduce them.

Does the auditor have to follow every requirement?

Paragraph 18 of ISA (UK) 200 requires the auditor to comply with every ISA (UK) relevant to the audit, meaning one that is in effect where the circumstances it deals with exist. Paragraph 22 then requires compliance with each requirement unless the whole standard is not relevant or the requirement is conditional and the condition does not exist. ISA (UK) 600 on component auditors, for example, has requirements that fall away if the group auditor does all the work.

Departures are allowed only in exceptional circumstances, where a specific procedure would be ineffective, and paragraph 23 then requires alternative procedures that achieve the aim of the requirement. Paragraph 20 prohibits the auditor from claiming compliance with the ISAs (UK) in the auditor’s report unless all relevant requirements have been met.

Which other FRC pronouncements carry weight?

The FRC also issues Practice Notes and Bulletins, and recognised bodies issue Statements of Recommended Practice (SORPs). These are persuasive rather than prescriptive. An auditor who does not consider and apply a relevant Practice Note or SORP should be prepared to explain how the standards have still been complied with. The Scope and Authority document adds that all relevant FRC pronouncements are likely to be taken into account when a court or regulator judges whether a practitioner’s work was adequate.

When do new versions take effect?

Each ISA (UK) states its own effective date, and ISA (UK) 200 permits early application unless the standard says otherwise. The FRC’s list notes that the standards are effective for periods commencing on or after 15 December 2019 unless otherwise stated. Later revisions include:

  • ISA (UK) 315 (Revised July 2020), for periods beginning on or after 15 December 2021;
  • ISQM (UK) 1, effective as of 15 December 2022;
  • ISA (UK) 600 (Revised September 2022), for group audits of periods beginning on or after 15 December 2023;
  • ISA (UK) 700, 701 and 720, revised in 2026 to shorten auditor’s reports, with ISA (UK) 700 effective for periods commencing on or after 15 December 2026.

How does this work on a group audit with an overseas subsidiary?

Illustration only. A UK parent has a subsidiary in another country audited by a local firm under the IAASB’s ISAs. The UK group auditor must be satisfied that the group audit as a whole complies with the ISAs (UK). The Scope and Authority document says overseas component auditors are not required to follow the UK additions, although the group auditor may refer to them in its instructions. Some UK additions bite directly on the group auditor instead. Paragraph 25 of ISA (UK) 600 requires confirmation that component auditors can comply with the relevant parts of the FRC’s Ethical Standard, and a UK paragraph added after paragraph 41 reminds the group auditor that negative confirmations are prohibited under ISA (UK) 505. See group audits and component auditors.

What mistakes are common?

  • Working from the IAASB handbook rather than the FRC’s version, and missing the shaded UK paragraphs.
  • Reading only the requirements and skipping the “A” paragraphs that ISA (UK) 200 says must be understood.
  • Using an out of date version. The FRC updates standards for conforming amendments; ISA (UK) 230, for example, is now published as Revised June 2016, Updated September 2025.
  • Treating smaller entity guidance as a lighter set of requirements. It is not.
  • Assuming Practice Notes can be ignored because they are not mandatory.

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Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.