Accounting estimates are the part of an audit where vouching alone stops working. A receivable impairment, a warranty provision, a fair value, the useful life of plant or a litigation provision depends on a method, data and assumptions rather than on a single invoice or contract. SA 540 gives the auditor a structured way to deal with that uncertainty without treating every estimate as automatically wrong or automatically high risk.
The standard's full title is SA 540, Auditing Accounting Estimates, Including Fair Value Accounting Estimates, and Related Disclosures. It is effective for audits of financial statements for periods beginning on or after 1 April 2009. ICAI's Engagement and Quality Control Standards repository, last updated on 13 May 2026, lists it in the 500 to 599 Audit Evidence series under that title, so this is the version that applies to current audits.
What the auditor must conclude
Paragraph 6 sets the objective: obtain sufficient appropriate audit evidence whether, in the context of the applicable financial reporting framework, (a) accounting estimates, including fair value accounting estimates, whether recognised or disclosed, are reasonable, and (b) the related disclosures are adequate. Both limbs matter. An estimate can sit within a reasonable range and still leave the audit incomplete if the note on estimation uncertainty is thin.
Two definitions in paragraph 7 frame the rest of the standard:
- Estimation uncertainty is the susceptibility of an accounting estimate and related disclosures to an inherent lack of precision in its measurement.
- Management bias is a lack of neutrality by management in the preparation and presentation of information.
Uncertainty is not the same as error. When an outcome later differs from the amount booked, the question is whether management used an appropriate method, suitable data and reasonable assumptions based on what was known at the reporting date.
Understanding how management made the estimate
Risk assessment starts with the reporting-framework requirements for the estimate and with how management identifies the transactions, events and conditions that need estimating. The auditor then understands how management actually makes the estimate: the method or model, the relevant controls, any use of a management's expert, the underlying assumptions, changes from the prior period and how estimation uncertainty has been assessed.
A good working paper for each material estimate answers five questions in plain language: what is being estimated, why an estimate is needed, what data drives it, whether the method changed from last year and what controls exist over the process.
Looking back at last year's estimates
Paragraph 9 requires the auditor to review the outcome of prior-period accounting estimates, or where applicable their subsequent re-estimation, for the purpose of identifying and assessing risks in the current period. The review is not meant to question judgments that were reasonable on the information then available.
Used properly, it is one of the most revealing procedures in the file. Suppose a company provided ₹8,00,000 for doubtful receivables at 31 March 2025, and write-offs and recoveries on those same debtors during 2025-26 show an actual loss of ₹11,50,000. The provision fell short by ₹3,50,000, or 43.75% of the amount booked. One shortfall may be explained by a single customer failure. If the prior year showed a similar gap, the pattern suggests optimistic assumptions, and the current-year provision needs harder challenge.
Deciding how much uncertainty is involved
The auditor evaluates the degree of estimation uncertainty and determines whether any estimate with high estimation uncertainty gives rise to a significant risk. Uncertainty tends to be higher where outcomes are hard to predict, significant assumptions drive the figure, observable inputs are limited or a specialised model is used.
The audit plan should scale with that assessment. A year-end accrual built from reliable invoices received after the year end needs a very different approach from a fair-value model for unquoted shares or a provision for a tax dispute with a wide range of possible outcomes.
The four responses in paragraph 13
In responding to the assessed risks, the auditor undertakes one or more of the following, taking into account the nature of the estimate:
| Response | What it involves | Works well for |
|---|---|---|
| 13(a) Events up to the report date | Determine whether events occurring up to the date of the auditor's report provide evidence about the estimate | Accruals settled soon after year end, receivables collected after the balance sheet date |
| 13(b) Test how management made it | Evaluate whether the measurement method is appropriate and the assumptions are reasonable, and test the data | Model-driven provisions and impairments |
| 13(c) Test controls plus substantive work | Test the operating effectiveness of controls over the estimate, together with appropriate substantive procedures | High-volume, system-generated estimates |
| 13(d) Auditor's point estimate or range | Develop an independent point estimate or range; a range must be narrowed, based on audit evidence, until all outcomes within it are considered reasonable | Estimates where management's process is weak or poorly documented |
Where valuation techniques, actuarial assumptions, engineering inputs or other specialist matters drive the estimate, the engagement team also considers whether it needs specialised skills or knowledge to carry out these responses.
Worked example: a warranty provision after a product change
A manufacturer sold 50,000 units in the year. Management booked its warranty provision using last year's historical claim rate of 2.0% and an average repair cost of ₹1,500 across all units:
Management's provision: 50,000 × 2.0% × ₹1,500 = ₹15,00,000.
During the year, however, 10,000 of those units came from a new product line that uses a component from a new supplier, and the average repair cost on the new line is ₹2,200. A weak audit response simply recomputes management's spreadsheet. A response built on paragraph 13 tests the sales and claims data, compares recent claims on the new line with the older pattern, and looks at claims received after the year end up to the report date.
Suppose that evidence supports a claim rate of 2.0% for the 40,000 legacy units and between 3.0% and 4.0% for the new line. The auditor's range is then:
| Component | Low end | High end |
|---|---|---|
| Legacy units: 40,000 × 2.0% × ₹1,500 | ₹12,00,000 | ₹12,00,000 |
| New line: 10,000 × 3.0% or 4.0% × ₹2,200 | ₹6,60,000 | ₹8,80,000 |
| Auditor's range | ₹18,60,000 | ₹20,80,000 |
Management's ₹15,00,000 sits ₹3,60,000 below the low end of the range and ₹5,80,000 below the high end. Before relying on the range, the auditor narrows it as paragraph 13(d) requires, for example by using actual post-year-end claim data on the new line. The gap to the nearest end of the narrowed range is then taken to the evaluation of misstatements and discussed with management. The same working paper should also consider whether the note on estimation uncertainty explains the new product risk.
Extra work when an estimate is a significant risk
For estimates that give rise to significant risks, paragraphs 15 to 17 add further requirements:
- Alternatives: evaluate how management considered alternative assumptions or outcomes and why it rejected them, or how it otherwise addressed estimation uncertainty.
- Significant assumptions: evaluate whether the significant assumptions used by management are reasonable.
- Intent and ability: where relevant, evaluate management's intent to carry out specific courses of action and its ability to do so, for example a plan to sell an asset that supports a lower impairment.
- Developing a range: if management has not adequately addressed the effects of estimation uncertainty, the auditor develops a range, where considered necessary, to evaluate reasonableness.
- Recognition and measurement: obtain evidence that management's decision to recognise or not recognise the estimate, and the measurement basis selected, comply with the framework.
Disclosures
Paragraphs 19 and 20 require evidence that disclosures about estimates meet the framework's requirements and, for estimates that give rise to significant risks, an evaluation of whether estimation uncertainty is adequately disclosed. In the warranty example, a note that says only "provision is based on past experience" would not tell a reader that a new product line with higher failure rates now drives a large part of the balance.
Reading estimates together for signs of bias
Paragraph 21 requires the auditor to review the judgments and decisions made by management in making estimates to identify whether there are indicators of possible management bias. Such indicators do not of themselves constitute misstatements. What matters is the pattern across estimates, not whether one estimate sits near one end of a reasonable range. Questions worth recording:
- Do assumptions repeatedly move in a direction that improves profit or a covenant ratio?
- Are model changes introduced only when they produce a favourable result?
- Are downside scenarios dismissed without persuasive evidence?
- Does the prior-period review show a consistent tendency to understate obligations or overstate asset values?
Written representations and documentation
Paragraph 22 requires written representations from management and, where appropriate, those charged with governance, on whether they believe the significant assumptions used in making accounting estimates are reasonable. Paragraph 23 requires the documentation to include the basis for the auditor's conclusions about the reasonableness of estimates that give rise to significant risks, and indicators of possible management bias, if any.
A practical documentation checklist for each material estimate:
- The estimate, its amount and the reporting requirement that applies.
- Management's method, data, controls, assumptions and any expert used.
- The prior-period outcome review and what it indicates for the current year.
- The assessed estimation uncertainty and whether it is a significant risk.
- The paragraph 13 response chosen and why it addresses the risk.
- Any auditor's point estimate or range, with the evidence used to narrow it.
- For significant risks, the work on alternatives, significant assumptions and intent and ability.
- The evaluation of disclosures, the bias review across estimates and the written representation obtained.
Mistakes that weaken the file
- Re-performing management's arithmetic without testing the data and assumptions behind it.
- Using hindsight to label every difference between a prior estimate and its outcome as an error.
- Applying the same procedures to low-uncertainty and high-uncertainty estimates.
- Accepting a management's expert or model output without understanding its inputs.
- Concluding on the amount and ignoring the disclosure of estimation uncertainty.
- Reviewing each estimate in isolation and missing a consistent optimistic tilt.
A strong SA 540 file does not try to prove that an estimate is mathematically exact. It shows, estimate by estimate, how the risk was assessed, which response was chosen, what evidence supported the conclusion on both amount and disclosure, and whether management's judgments stayed neutral.
Updated on 27 September 2026: retitled; added paragraph references to SA 540, the effective date, a prior-period review example, a warranty range calculation and the written representation and documentation requirements.
