Performance materiality and tolerable misstatement both sit below overall materiality and both exist to keep undetected errors from adding up to a material misstatement, but they operate at different levels of the audit and, under some standards, do not both exist. In the performance materiality vs. tolerable misstatement comparison, the cleanest way to keep them straight is this: under ISA and AICPA standards, performance materiality is a planning-level buffer set below overall materiality, and tolerable misstatement is the tighter, account-specific cap applied during sampling. Under PCAOB standards, the term “performance materiality” does not appear, and “tolerable misstatement” carries both roles.
What Each Term Means
Performance materiality, as defined by ISA 320, is the amount the auditor sets below overall materiality to reduce the chance that the total of uncorrected and undetected misstatements exceeds the overall figure.1International Auditing and Assurance Standards Board. ISA 320 (Revised and Redrafted) – Materiality in Planning and Performing an Audit It is a planning number. It exists because if an auditor tested every account to the full overall materiality level, the individual undetected errors could combine into something that blows past the overall threshold once aggregated.
Tolerable misstatement is the maximum error the auditor will accept in a specific account balance or class of transactions before concluding that the balance is misstated. Its most direct effect is on sample size. PCAOB AS 2315 states the relationship plainly: a smaller tolerable misstatement for a given population requires a larger sample to maintain the same level of assurance.2Public Company Accounting Oversight Board. AS 2315 – Audit Sampling Set tolerable misstatement at $40,000 for an accounts payable population and you test substantially more invoices than if you set it at $80,000.
So the terms describe different things. One is a firm-wide planning buffer for the engagement. The other is an account- or population-level operational limit that drives testing.
Why the Standards Diverge
The reason the two concepts get tangled is that different sets of auditing standards use different vocabulary for what is essentially the same idea.
The PCAOB’s AS 2105 requires auditors to set “tolerable misstatement” below overall materiality so that the combined effect of undetected and uncorrected errors stays at an acceptably low level.3Public Company Accounting Oversight Board. AS 2105 – Consideration of Materiality in Planning and Performing an Audit The standard never mentions performance materiality. In a PCAOB engagement, tolerable misstatement is the single reduced threshold below overall materiality, and it drives both risk assessment and the design of substantive procedures at the account level.
ISA 320 and the AICPA’s AU-C 320 use a two-tier structure. Performance materiality is set below overall materiality as a planning buffer, and tolerable misstatement is then derived from performance materiality and applied at the individual sampling population.1International Auditing and Assurance Standards Board. ISA 320 (Revised and Redrafted) – Materiality in Planning and Performing an Audit Under this framework the two figures can differ, and tolerable misstatement for a given account is typically equal to or less than performance materiality.
Many firms use both terms in their internal methodologies regardless of which standard governs. The conceptual hierarchy holds either way. Overall materiality sits at the top. A reduced planning threshold sits below it. Account-specific limits sit below that. The labels depend on whose work paper you are reading.
How They Fit Together
Every audit operates on the same cascading structure once the terminology is stripped away:
- Overall materiality is the maximum misstatement that would influence a reasonable user’s decisions, set as a percentage of a benchmark such as pretax income, total revenue, or total assets. ISA 320 offers 5% of profit before tax for a manufacturing company or 1% of total revenue for a not-for-profit entity as illustrative starting points.1International Auditing and Assurance Standards Board. ISA 320 (Revised and Redrafted) – Materiality in Planning and Performing an Audit
- Performance materiality (ISA/AICPA) or the reduced tolerable misstatement level (PCAOB) is set below overall materiality as a buffer.
- Account-level tolerable misstatement is the maximum error accepted in a specific population for sampling. It drives sample size directly and, under ISA/AICPA, is typically set at or below performance materiality.
- The clearly trivial threshold sits at the bottom, marking the de minimis amount below which individual errors are not accumulated on the summary of uncorrected misstatements. ISA 450 requires accumulation of everything except items that are clearly trivial, and firms commonly set that line around 5% of overall materiality.
Each level depends on the one above it, and a mistake at any level cascades downward.
Setting the Numbers
A common rule of thumb sets performance materiality between 50% and 75% of overall materiality. The specific percentage moves inversely with risk. An entity with weak internal controls, complex accounting estimates, or a history of audit adjustments pushes the percentage toward 50%, which produces a smaller dollar amount and more extensive testing. A well-controlled entity with clean prior audits might justify 75%. This is professional judgment, not a formula, and the auditor must be able to defend the percentage if a regulator or peer reviewer asks about it.
Take a company with overall materiality of $1,000,000. Setting performance materiality at 60% produces a $600,000 threshold. Every substantive procedure the audit team designs now has to be precise enough that the combined undetected misstatements across all accounts stay below $600,000 rather than $1,000,000. That tighter target is the entire reason performance materiality exists.
Tolerable misstatement then gets allocated across every significant account balance and transaction class. The allocation is not simply proportional to account size. Accounts with higher assessed risk of misstatement — inventory with complex valuation assumptions, revenue with multiple performance obligations, estimates requiring significant management judgment — typically receive a lower tolerable misstatement, which forces more testing.
Why the Allocated Amounts Can Exceed the Parent Figure
A quirk of allocation catches people off guard. The sum of allocated tolerable misstatements across accounts often exceeds the overall performance materiality figure. ISA 600 acknowledges this in the group audit context: the aggregate of component materiality levels may exceed overall group materiality because it is statistically improbable that every account will be misstated by its full tolerable amount simultaneously. The over-allocation is standard practice, not an error.
Assume performance materiality of $600,000 spread across four major accounts. Accounts receivable might get $200,000, inventory $250,000, fixed assets $150,000, and accounts payable $175,000. The total is $775,000, well above the $600,000 planning figure. The auditor accepts this because the chance of all four accounts being simultaneously misstated at their maximum tolerable level is remote. Rigidly capping the sum at $600,000 would force testing far beyond what reasonable assurance requires.
What Each Threshold Does During Fieldwork
Once the numbers are set, they become operational limits. Tolerable misstatement is a direct input to sample size calculations. Every misstatement above the clearly trivial threshold gets recorded and, for sampled populations, projected across the full population. If projected misstatements in an account stay within its tolerable misstatement, the account passes. If they exceed it, the auditor expands the sample, performs alternative procedures, or asks the client to record an adjustment.
At the end of fieldwork, all projected and known misstatements are aggregated onto a single schedule. The auditor evaluates that aggregate against performance materiality (ISA) or tolerable misstatement (PCAOB), weighing both quantitative size and qualitative significance. PCAOB AS 2105 frames this evaluation in terms of whether uncorrected misstatements, individually or combined, are material in relation to the financial statements as a whole.3Public Company Accounting Oversight Board. AS 2105 – Consideration of Materiality in Planning and Performing an Audit If the aggregate stays below the reduced threshold, the auditor has reasonable assurance that the statements are free from material misstatement at the overall level. If it exceeds the threshold, the engagement team must expand testing or require an adjustment.
This is where the buffer earns its keep. Because the auditor planned and tested to a number below overall materiality, there is room for some undetected misstatement without pushing total error above the level that matters to financial statement users.
The Short Version
Performance materiality is the reduced planning-level threshold set below overall materiality to buffer against the accumulation of undetected errors across the whole engagement. Tolerable misstatement is the account-level or population-level cap that drives sample sizes and passes/fails individual balances. Under ISA and AICPA standards both terms are used, with tolerable misstatement derived from performance materiality. Under PCAOB standards, tolerable misstatement is the only term used, and it plays both roles. Which vocabulary you should be using depends entirely on which set of standards governs the engagement.