ISA 450 — Evaluation of Misstatements Identified During the Audit: Complete Guide

Key Takeaways

ISA 450 requires the auditor to accumulate all misstatements identified during the audit, other than those that are clearly trivial. This includes misstatements in amounts, classifications, presentations, and disclosures.
Misstatements are categorised as factual (no doubt about the error), judgmental (differences in estimates or accounting policy application), or projected (the auditor's best estimate of misstatements in populations based on sampling results).
"Clearly trivial" is not another expression for "not material" — it is a wholly different, smaller order of magnitude. In practice, clearly trivial is typically set at 3–5% of overall materiality.
The auditor must communicate all accumulated misstatements to management on a timely basis and request correction. If management refuses to correct, the auditor must understand the reasons and consider whether management's judgment indicates possible bias.
Before forming the opinion, the auditor must reassess materiality (ISA 320) and then evaluate whether uncorrected misstatements are material, individually or in aggregate, considering both size and nature.
Uncorrected misstatements and the effect on the opinion must be communicated to those charged with governance (ISA 260), and the auditor must obtain a written representation that management considers the effects of uncorrected misstatements to be immaterial.

What is ISA 450?

ISA 450, titled "Evaluation of Misstatements Identified During the Audit," governs what happens after the auditor finds errors. Every audit finds misstatements — the question is what to do with them. ISA 450 provides the framework for accumulating, communicating, evaluating, and ultimately deciding whether uncorrected misstatements require the auditor to modify the opinion.

The standard is the companion to ISA 320 (Materiality). ISA 320 sets the threshold; ISA 450 evaluates findings against that threshold. Together, they form the mechanism by which the auditor translates audit evidence into the opinion on the financial statements.

Types of Misstatements

ISA 450.A1 identifies the sources, and ISA 450.A3 distinguishes three categories that are useful for evaluation and communication:

Type	Description	Example
Factual misstatements	Misstatements about which there is no doubt — clear errors in data, omissions, or breaches of reporting standards	An invoice recorded at the wrong amount; a required disclosure omitted entirely; depreciation calculated using the wrong rate
Judgmental misstatements	Differences arising from management's judgments that the auditor considers unreasonable — in accounting estimates or policy application	An allowance for doubtful debts that falls outside the auditor's reasonable range; a provision measured using assumptions the auditor considers inappropriate
Projected misstatements	The auditor's best estimate of misstatements in a population, projected from misstatements found in a sample	Sampling of 50 invoices reveals a 2% overstatement error rate; projected to the full population, the estimated misstatement is €45,000

This categorisation is not required by the standard but is recommended as a practical tool for communication with management and those charged with governance.

Accumulating Misstatements

ISA 450.5 requires the auditor to accumulate all misstatements identified during the audit, other than those that are clearly trivial.

The "clearly trivial" threshold

ISA 450.A2 provides critical guidance: "clearly trivial" is not another expression for "not material." Matters that are clearly trivial are of a wholly different (smaller) order of magnitude than materiality — they are matters that are clearly inconsequential whether taken individually or in aggregate, and whether judged by any criteria of size, nature, or circumstances.

When there is any uncertainty about whether something is clearly trivial, it is not clearly trivial and must be accumulated.

In practice, firms typically set the clearly trivial threshold at 3–5% of overall materiality (sometimes up to 10%), though this varies by firm methodology. The threshold must be documented.

Nature matters, not just amount

A misstatement of €500 in a company with overall materiality of €100,000 might be clearly trivial by amount — but not if it involves a related party transaction, executive compensation, or a potential fraud indicator. Always consider whether the nature or circumstances of a misstatement make it significant regardless of its monetary size. A systematic error in a control that produces small individual misstatements but indicates a pervasive control failure is never clearly trivial.

Considering Misstatements as the Audit Progresses

ISA 450.6–7 requires the auditor to consider, during the audit, whether the nature and circumstances of identified misstatements indicate that other misstatements may exist that, when taken together with accumulated misstatements, could be material.

If the aggregate of misstatements accumulated during the audit approaches materiality, the auditor must consider whether additional audit procedures are needed. This is the early warning system — if you are finding significant misstatements in early fieldwork, the risk assessment may need revision and the planned procedures may be insufficient.

If the nature of identified misstatements suggests systemic issues (e.g., a breakdown in a control, an incorrect application of an accounting policy across all transactions), the auditor should determine whether the audit strategy and plan need to be revised.

Communication and Correction

Communication with management

ISA 450.8 requires the auditor to communicate all accumulated misstatements to the appropriate level of management on a timely basis, and to request that management correct those misstatements.

"Appropriate level" means the level that has responsibility and authority to evaluate the misstatements and take corrective action. For routine errors, this may be the finance director or controller. For judgmental misstatements involving significant estimates, this may be the CFO or CEO.

Why timeliness matters

Timely communication gives management the opportunity to correct misstatements before the financial statements are finalised. It also allows the auditor to observe management's attitude toward corrections — a management team that consistently refuses to correct errors, even when it would be straightforward to do so, may be exhibiting a pattern of bias that the auditor should consider under ISA 240 (Fraud).

If management corrects the misstatements

Corrected misstatements are removed from the summary of uncorrected misstatements. However, the auditor should consider whether the corrected misstatement indicates a control deficiency that should be communicated under ISA 265.

If management refuses to correct

The auditor must understand management's reasons. The reasons are relevant to the overall evaluation of management's judgment and to the auditor's consideration of potential management bias.

Evaluating Uncorrected Misstatements

Reassess materiality first

ISA 450.10 requires the auditor, before evaluating uncorrected misstatements, to reassess the materiality determined under ISA 320. Since materiality at planning was often based on estimates (budgeted profit, for example), the auditor must confirm whether the materiality level remains appropriate based on actual results.

The evaluation

ISA 450.11 requires the auditor to determine whether uncorrected misstatements are material, individually or in aggregate. The evaluation considers:

Size — does the aggregate of uncorrected misstatements exceed materiality? If the aggregate approaches but does not exceed materiality, the risk that undetected misstatements (which always exist due to sampling and other limitations) could push the total above materiality must be considered.

Nature — some misstatements may be material due to their qualitative characteristics regardless of amount. A misstatement that affects a loan covenant, reverses the direction of a trend, converts a profit to a loss, affects related party disclosures, or relates to management compensation may be material at amounts below quantitative materiality.

Circumstances — the particular context of each misstatement, including its effect on key ratios, compliance with regulatory requirements, and the impact on users' decision-making.

Prior-period uncorrected misstatements — the auditor must also consider whether uncorrected misstatements from prior periods affect the current period's financial statements. Opening balances carry forward, and prior-period misstatements that "reverse" in the current period still matter because both periods may be misstated.

Can misstatements offset each other?

ISA 450.A14 addresses this: if an individual misstatement is judged to be material, it is unlikely that it can be offset by other misstatements. Even if revenue is overstated by €50,000 and expenses are overstated by €50,000 (resulting in zero net effect on profit), both the revenue and expense lines are misstated — and users who rely on those individual figures are misled. Offsetting of immaterial misstatements within the same account balance may be appropriate, but only after considering whether further undetected misstatements might exist.

Communication with Those Charged with Governance

ISA 450.12–13 requires the auditor to communicate to those charged with governance:

Uncorrected misstatements and the effect they may have, individually or in aggregate, on the opinion in the auditor's report. The communication must identify material uncorrected misstatements individually.
The effect of uncorrected misstatements related to prior periods on the relevant classes of transactions, account balances, or disclosures, and on the financial statements as a whole.

The auditor must also request that those charged with governance correct the uncorrected misstatements.

Written Representation

ISA 450.14 requires the auditor to obtain a written representation from management (and, where appropriate, those charged with governance) that they believe the effects of uncorrected misstatements are immaterial, individually and in the aggregate, to the financial statements as a whole. A summary of the uncorrected misstatements must be included in or attached to the written representation.

This representation serves two purposes: it formally records management's acknowledgment of the uncorrected misstatements, and it provides the auditor with evidence that management has evaluated the effect and concluded it is immaterial. If management will not provide this representation, the auditor must consider the implications under ISA 580.

Documentation

ISA 450.15 requires documentation of:

The clearly trivial threshold — the amount below which misstatements are not accumulated.
All misstatements accumulated during the audit and whether they have been corrected.
The auditor's conclusion as to whether uncorrected misstatements are material, individually or in aggregate, and the basis for that conclusion.

ISA 450 in Your Jurisdiction

Netherlands. COS 450 follows ISA 450 closely. AFM inspections regularly examine the summary of uncorrected misstatements and evaluate whether the auditor's conclusion on materiality is well-supported. The AFM has noted deficiencies where auditors fail to consider the qualitative aspects of misstatements, or where the aggregate of uncorrected misstatements approaches materiality without the auditor performing additional procedures.

Germany. IDW PS 450 adapts ISA 450. The Prüfungsbericht requires disclosure of identified misstatements and their evaluation, making the German documentation requirements particularly rigorous. The WPK's inspections focus on whether the evaluation of misstatements is consistent with the materiality levels documented under ISA 320.

United Kingdom. ISA (UK) 450 is substantively aligned with ISA 450. The FRC's inspections have identified cases where auditors do not sufficiently challenge management's reasons for declining to correct misstatements, and where the evaluation of aggregate misstatements approaching materiality is insufficiently rigorous.

France. NEP 450 implements ISA 450 within the French statutory framework. French practice requires the commissaire aux comptes to present a summary of proposed adjustments (ajustements proposés) and uncorrected misstatements (anomalies non corrigées) in the lettre de direction, which is a key deliverable of the audit process.

Frequently Asked Questions

What happens if uncorrected misstatements exceed materiality?

If the auditor concludes that uncorrected misstatements, individually or in aggregate, are material, the auditor must either obtain correction from management or modify the audit opinion under ISA 705. A qualified opinion is issued if the misstatement is material but not pervasive; an adverse opinion is issued if it is material and pervasive.

Must the auditor report misstatements below the clearly trivial threshold?

No. Misstatements below the clearly trivial threshold need not be accumulated or communicated. However, the threshold must be set at a level that is a wholly different order of magnitude from materiality, and any uncertainty about whether an item is clearly trivial means it must be accumulated.

How do projected misstatements work in the evaluation?

Projected misstatements are the auditor's best estimate of the total misstatement in a population based on errors found in a sample. They are included in the summary of accumulated misstatements at their projected amount (not just the amount actually found in the sample). The auditor should also consider whether the projection indicates a systematic error requiring investigation.

Does the auditor need to consider prior-year uncorrected misstatements?

Yes. The auditor must consider the effect of prior-period uncorrected misstatements on the current period's financial statements. Some prior-year misstatements may reverse in the current year (e.g., an accrual that was understated last year increases this year's expense), while others may persist in the balance sheet.