IAS 8: Policy, Estimate or Error, and Why the Treatment Differs So Much

Three things can change the numbers in a set of financial statements: the policy, the estimate, or the correction of something that was wrong. IAS 8 governs all three, and the treatments could not be more different. One restates the comparatives. One never touches a prior period. One restates the comparatives and is kept out of current-year profit entirely.

Telling them apart is the most examined point in the standard and the one most commonly got wrong in practice. The discriminator is not how large the adjustment is, or how surprising. It is narrower and more technical than that.

First, the title, because it is about to change

For periods beginning before 1 January 2027 the standard is IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors. For periods beginning on or after that date, when IFRS 18 is applied, it becomes IAS 8 Basis of Preparation of Financial Statements.

The reason is counterintuitive. IFRS 18 replaces IAS 1, and rather than being narrowed, IAS 8 became broader: it absorbed several of the general requirements that used to live in IAS 1, including fair presentation, compliance with IFRS Accounting Standards, going concern and the accrual basis. Paragraph 54J states that an entity applies those amendments when it applies IFRS 18, so the retitling arrives on the same date. The IFRS Foundation standards list already shows the new title because that list reflects standards as issued, including amendments not yet effective. The UK Endorsement Board approved IFRS 18 for UK adoption on 10 December 2025, effective for periods beginning on or after 1 January 2027 with earlier application permitted, so the UK date is the same. Our guide to IFRS 18 presentation and disclosure covers the wider change.

For a 2026 year end, use the old title.

The hierarchy, in four tiers

Students usually flatten this into a single list. It is not a list; it is a ranking, and only the first three tiers are mandatory.

• Tier 1, paragraph 7. If an IFRS specifically applies, apply it. There is no judgement to exercise.
• Tier 2, paragraph 10. If none applies, management uses judgement to develop a policy giving relevant and reliable information.
• Tier 3, paragraph 11. In doing so, refer in descending order to the requirements in IFRSs dealing with similar and related issues, and then to the definitions, recognition criteria and measurement concepts in the Conceptual Framework.
• Tier 4, paragraph 12. Management may also consider the most recent pronouncements of other standard-setters using a similar conceptual framework, other accounting literature and accepted industry practices, but only to the extent these do not conflict with tier 3.

Tier 4 is permissive and expressly subordinate. Citing industry practice as though it ranked alongside the Conceptual Framework is a straightforward error.

Changing a policy is also constrained. Paragraph 14 permits it only where a change is required by an IFRS, or where the change results in information that is reliable and more relevant. Note the direction of travel: a voluntary change must improve the information. There is no free choice. And under paragraph 16, applying a policy to transactions that are new or substantively different is not a change in accounting policy at all.

The three categories, and what actually separates them

A policy

A policy is the recognition basis, measurement basis or presentation chosen. A change is applied retrospectively. Paragraph 22 requires the opening balance of each affected component of equity to be adjusted for the earliest prior period presented, with the other comparative amounts restated as if the new policy had always been applied.

An estimate

Since the Definition of Accounting Estimates amendment, effective for periods beginning on or after 1 January 2023, paragraph 5 defines accounting estimates as monetary amounts in financial statements that are subject to measurement uncertainty. Paragraph 32 ties the two concepts together: an entity develops an accounting estimate to achieve the objective set out by the accounting policy. The estimate serves the policy; it is not an alternative to it.

Paragraph 34 is the operative sentence: by its nature, a change in an accounting estimate does not relate to prior periods and is not the correction of an error. Changes are recognised prospectively in profit or loss of the current period and future periods if affected. Comparatives are never restated.

An error

Paragraph 5 defines prior period errors as omissions from, and misstatements in, prior period financial statements arising from failing to use, or misusing, reliable information that was available and could reasonably be expected to have been obtained. That final clause is the whole test. Material errors are corrected retrospectively under paragraph 42, and paragraph 46 adds the part most often missed: the correction is excluded from profit or loss for the period in which the error is discovered.

The trap

The same fact pattern falls into different categories depending on what information was available at the time. A receivables provision revised because a customer has just failed is a change in estimate. The same provision revised because the entity had a liquidation notice on file and ignored it is an error. Nothing about the amount changes; only the availability of the information.

Paragraph 35 supplies the tiebreak. A change in the measurement basis is a change in policy rather than estimate, but where it is difficult to distinguish the two, the change is treated as a change in estimate, which conveniently means no restatement.

One specific trap worth naming: a change from straight line to reducing balance depreciation is routinely called a change of policy. It is not. Under IAS 16 and IAS 38 a change in depreciation or amortisation method is a change in estimate, handled prospectively. See our guide to IAS 16 property, plant and equipment for how that interacts with revaluation and component depreciation.

Two terms that are not interchangeable

Paragraph 5 defines both separately. Retrospective application means applying a new accounting policy to transactions as if that policy had always been applied. Retrospective restatement means correcting the recognition, measurement and disclosure of amounts as if a prior period error had never occurred. Same mechanics, different trigger, different disclosure note. Policies are applied; errors are restated. Writing that you will restate the policy loses marks.

Worked example: an error and an estimate, side by side

Part A, a prior period error

Entity A has a year ended 31 December 20X5. During 20X5 it discovers that closing inventory at 31 December 20X4 was overstated by £90,000 because one warehouse was counted twice. The tax rate is 20 per cent and the error is material.

Cost of sales for 20X4 was understated by £90,000, so profit before tax was overstated by £90,000 and tax expense overstated by £18,000 (90,000 at 20 per cent). Profit for 20X4 was therefore overstated by £72,000.

The 20X4 comparative statement of financial position is restated: inventory down £90,000, current tax liability down £18,000, retained earnings down £72,000. The adjustment to opening balances at 1 January 20X5 is to debit opening retained earnings £72,000 and the current tax liability £18,000, crediting inventory £90,000.

Here is the part students miss. The error self-reverses. With a corrected, lower opening inventory, 20X5 cost of sales falls by £90,000, so 20X5 profit before tax is £90,000 higher than the uncorrected books showed. Cumulative two-year profit is unchanged; only its allocation between periods moves. And under paragraph 46 none of the £72,000 correction passes through 20X5 profit or loss.

Part B, a change in estimate

The same entity acquired a machine on 1 January 20X1 for £500,000, estimating a ten-year life, nil residual value, straight line. On 1 January 20X4 the remaining useful life is revised to four years.

Original depreciation was £50,000 a year, so accumulated depreciation at 31 December 20X3 is £150,000 and the carrying amount is £350,000. Revised depreciation is £350,000 over four years, or £87,500 a year. Check: 87,500 times four is 350,000, so the asset is fully depreciated at the end of 20X7.

20X1 to 20X3 are not restated. There is no opening equity adjustment and no change to any comparative. Set that against Part A: similar arithmetic, entirely different treatment, and the contrast is the examinable insight.

When retrospective application is impracticable

Paragraph 5 defines impracticable as being unable to apply a requirement after making every reasonable effort to do so, and gives three triggers: the effects cannot be determined; application requires assumptions about what management intent would have been in that period; or it requires significant estimates that cannot be objectively distinguished from information available with hindsight.

Two different reliefs follow. Under paragraph 24, where the period-specific effects cannot be determined, apply the new policy to carrying amounts as at the beginning of the earliest period for which retrospective application is practicable, with a corresponding adjustment to opening equity. Under paragraph 25, where the cumulative effect cannot be determined, apply the new policy prospectively from the earliest date practicable. Paragraphs 43 to 47 mirror both reliefs for error corrections.

The UK position and FRS 102

IAS 8 is part of UK-adopted international accounting standards. The 2023 estimates amendment was adopted by the UK Endorsement Board on 30 November 2022, alongside the IAS 1 disclosure of accounting policies amendment and the IAS 12 single-transaction deferred tax amendment.

The FRS 102 equivalent is Section 10, Accounting Policies, Estimates and Errors, and it is structurally close to IAS 8 with one genuine UK difference. The hierarchy in 10.5 requires management to refer to and consider the applicability of listed sources in descending order, and that hierarchy includes Statements of Recommended Practice. There is no SORP analogue in IAS 8, which matters for charities, housing associations and other SORP-following entities. Paragraph 10.6 then mirrors the permissive tier. Paragraph 10.11(d) provides that all other changes in accounting policy are accounted for retrospectively.

One honest note on the FRS 102 periodic review, effective for periods beginning on or after 1 January 2026: it did not change Section 10 in substance. The headline changes were leases and revenue, as set out in our guide to the FRS 102 periodic review. If you are looking for what changed on policies, estimates and errors, the answer is effectively nothing.