SA 540 governs auditing accounting estimates — provisions, impairment calculations, fair value measurements, actuarial valuations — where no single verifiable number exists to check the balance against. The standard requires the auditor to understand the method, the data, and the assumptions management used to arrive at the estimate, and then respond using one or a combination of three approaches: testing management's process, developing an independent point estimate or range, or reviewing subsequent events that provide evidence about the outcome. Which approach fits depends on how much estimation uncertainty exists and how complex the method is — not a fixed choice applied the same way to every estimate.
The three response options
| Approach | When it fits | What it actually involves |
|---|---|---|
| Test management's process | The method is reasonable and well-understood, and the data/assumptions can be independently evaluated | Checking the data feeding the model, evaluating the reasonableness of key assumptions, recalculating the arithmetic |
| Develop an independent estimate or range | The auditor has the expertise to build a comparison point, or wants to corroborate management's figure independently | Using available data to build an auditor-derived estimate and comparing it to management's — a material gap between the two itself becomes a finding |
| Review subsequent events | The outcome becomes known, or substantially clearer, between the balance sheet date and the audit report date | E.g. a litigation provision where the case actually settles before the report is signed — the settlement is the best evidence of what the provision should have been |
Evaluating for management bias, not just arithmetic accuracy
An estimate can be internally consistent and arithmetically correct while still reflecting bias — a pattern of assumptions that each, individually, lean toward the outcome management prefers (a lower provision, a higher valuation). SA 540 specifically requires looking at estimates in aggregate across the engagement for this pattern, not evaluating each one in isolation, because a single biased assumption might look like reasonable judgment on its own while a consistent pattern across several estimates is a different and more serious signal.
A change in an estimation method or a key assumption from the prior year, with no change in the underlying facts justifying it, is a specific red flag SA 540 calls attention to — particularly where the change moves the estimate in a direction favourable to reported results.
What drives how much work an estimate needs
- 01How much estimation uncertainty existsA straightforward depreciation calculation carries far less estimation uncertainty than a discounted cash flow valuation with multiple unobservable inputs — the audit response should scale with that difference.
- 02How complex the estimation method isA complex model (actuarial, discounted cash flow) often needs an auditor's expert, per SA 620, rather than the engagement team evaluating it unaided.
- 03Whether the estimate is a significant riskWhere SA 315 identified the estimate as a significant risk, SA 540 requires specifically evaluating how management considered alternative assumptions or outcomes, not just accepting the single figure presented.
This is practical guidance written for audit teams, not an authoritative statement of any standard or statute. Standards, forms and timelines change. Check the current text issued by the ICAI and the relevant authority before relying on anything here in an audit file.
Related resources
- Payroll & employee costThe gratuity provision that was computed on the wrong salary baseThe actuary had valued the obligation correctly. The data file feeding the actuary had the wrong number in it for every employee.
- Fixed assets & capexImpairment testing for fixed assets: a practical approachThe impairment indicators that actually matter for a mid-market client, when a formal test is genuinely warranted, and how to test management's recoverable amount workings.
- Revenue, receivables & cut-offRevenue recognition testing in a statutory auditThe transfer-of-control test that governs when a sale is recognised, the misstatement patterns that recur in practice, and what evidence ties a recognised sale to an underlying document.
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