Misstatement Tracker
United Kingdom

ISA 450 misstatement evaluation in United Kingdom: ISA (UK) 450

ISA (UK) 450 mirrors the international standard in substance but sits within the FRC's broader framework of audit quality expectations that shape how UK auditors apply it in practice. The FRC adopted ISA (UK) 450 as part of its June 2016 suite of auditing standards, with additional UK-specific paragraphs that reflect the particular regulatory environment. The most significant UK addition is the enhanced communication requirement with those charged with governance. Under ISA (UK) 450.12-1, the auditor must request that management correct all misstatements accumulated during the audit, not just those above a certain threshold. This means the clearly trivial threshold acts as a documentation filter (items below it need not appear on the schedule) rather than a communication filter (items above it must be discussed). In practice, most UK audit firms communicate the full misstatement schedule to the audit committee and ask for a formal response on each uncorrected item. The UK audit market operates under a dual regulatory structure since the FRC took on direct oversight of PIE audits while the professional bodies (ICAEW, ICAS, CPA Ireland, and Chartered Accountants Ireland for Northern Ireland engagements) regulate non-PIE audits. For PIE audits, the FRC's Audit Quality Review (AQR) team inspects engagement files annually and publishes findings on misstatement evaluation as a recurring theme. For non-PIE audits, the ICAEW's Quality Assurance Department (QAD) conducts monitoring visits. Both regulators have flagged misstatement accumulation as an area requiring improvement, making it important for UK auditors to demonstrate a thorough ISA (UK) 450 process on every engagement.

Regulatory context: Financial Reporting Council (FRC)

The FRC's annual Audit Quality Inspection reports consistently identify ISA 450 application as an area for improvement. The 2023/24 inspection cycle found that auditors needed to improve their evaluation of uncorrected misstatements in 18% of PIE audits reviewed. The specific findings included: failure to assess whether uncorrected misstatements, individually or in aggregate, were material to the financial statements; insufficient consideration of the qualitative nature of misstatements (for example, misstatements affecting compliance with debt covenants or regulatory capital requirements); and inadequate documentation of the rationale for concluding that uncorrected misstatements were not material when their aggregate approached materiality. The FRC expects auditors to document a clear, reasoned evaluation under ISA (UK) 450.11 that goes beyond comparing the total to materiality. The FRC's Thematic Review on Materiality (published 2017, updated guidance in 2022) specifically addressed the interaction between materiality and misstatement evaluation. The review found that some auditors set performance materiality at a level that did not leave sufficient headroom for expected misstatements. When actual misstatements exceeded performance materiality, auditors were forced to either expand testing (which some did not do) or conclude that the uncorrected misstatements were immaterial without adequate basis. The FRC's position is that performance materiality should be set with reference to expected misstatements, and if actual misstatements exceed the level anticipated, the auditor must reassess the audit approach under ISA (UK) 320.12.

Practical guidance for United Kingdom

UK practitioners should align their ISA (UK) 450 process with the FRC's published expectations. Start by documenting the clearly trivial threshold in the audit strategy and applying it consistently to every identified misstatement. The FRC expects to see a clearly trivial threshold that is "clearly inconsequential" in both amount and nature. Most UK firms set this at 3% to 5% of overall materiality. Next, accumulate all misstatements above clearly trivial on a schedule that separates factual, judgmental, and projected categories. For each projected misstatement, document the extrapolation methodology and the sampling risk component. The FRC has criticised auditors who record the known error from the sample without projecting it across the population. When evaluating the aggregate of uncorrected misstatements under ISA (UK) 450.11, document both the quantitative assessment (comparing the aggregate to overall materiality) and the qualitative assessment (considering the nature, cause, and direction of misstatements). The FRC expects the qualitative assessment to cover at least: whether the misstatements affect key performance indicators or metrics referenced in the strategic report; whether they affect compliance with loan covenants or regulatory requirements; whether they indicate a pattern that suggests further undetected misstatements; and whether correction of the misstatements would change the trend of reported results.

Audit expectations

The AQR's published findings indicate that inspectors expect to see a completed misstatement schedule that ties to the audit completion memorandum, a documented evaluation under ISA (UK) 450.11 with both quantitative and qualitative components, evidence that all uncorrected misstatements were communicated to those charged with governance, and a documented response from those charged with governance explaining why they did not correct each item. The FRC specifically looks for evidence that the engagement partner personally reviewed the misstatement schedule and considered whether the aggregate of uncorrected misstatements required a modification to the auditor's report. For UK engagements where the entity prepares financial statements under FRS 102 rather than IFRS, the same ISA (UK) 450 requirements apply. The standard does not change based on the financial reporting framework. However, FRS 102 introduces some specific measurement differences (for example, the option to measure investment property at fair value through other comprehensive income under Section 16) that affect how misstatements flow through the financial statements.

United Kingdom-specific considerations

UK audit engagements frequently involve Companies Act 2006 considerations that interact with ISA (UK) 450. Section 393 of the Companies Act requires that the auditor's report states whether the financial statements give a true and fair view. Uncorrected misstatements that are individually or aggregately material prevent the auditor from issuing an unqualified opinion. Section 498 requires the auditor to report on certain matters by exception, including whether adequate accounting records have been kept. A high volume of misstatements, even if individually immaterial, may indicate weaknesses in the accounting records that trigger a Section 498 reporting obligation. UK auditors must also consider the interaction between misstatement evaluation and the extended auditor's report for PIE audits. ISA (UK) 700 requires the auditor to report on key audit matters, materiality, and the scope of the audit. If uncorrected misstatements relate to a key audit matter, the auditor should consider whether the description of the key audit matter in the auditor's report needs to address the misstatement and its effect. The FRC has made clear that the extended auditor's report should provide meaningful information about the audit, and a significant uncorrected misstatement in a key audit area that goes unmentioned raises questions about the transparency of the report.

Common inspection findings

Auditors failed to project known errors from samples across the untested population, recording only the errors found in the sample on the misstatement schedule.

The qualitative evaluation of uncorrected misstatements was absent or limited to a generic statement that "misstatements do not affect the true and fair view" without analysis of specific effects.

Engagement teams did not reassess performance materiality or extend audit procedures when accumulated misstatements exceeded the level anticipated in the audit strategy.

Communication to those charged with governance did not itemise individual uncorrected misstatements as required by ISA (UK) 450.12, instead presenting only an aggregated net figure.

The clearly trivial threshold was set but not consistently applied, with some misstatements below the threshold appearing on the schedule while others above it were excluded without documented rationale.