Key Takeaways
- ISA 600 (Revised) requires component performance materiality to be lower than group materiality to reduce aggregation risk — the risk that individually immaterial misstatements across components aggregate to a material amount at the group level (ISA 600 (Revised) para. 30).
- The "significant component" classification has been removed. ISA 600 (Revised) replaces it with a risk-based scoping model where every component receiving audit procedures on disaggregated financial information must have a component performance materiality.
- Most mid-tier firms apply 60–85% of group materiality per component, with 75% as the typical starting point. The percentage is adjusted for the number of components and their individual risk profiles.
- Different components can receive different materiality amounts (ISA 600 (Revised) para. A79). Higher-risk components get a lower allocation; low-risk or dormant components get a higher allocation.
- The group engagement team must also determine a communication threshold (typically 5% of component performance materiality) above which misstatements at the component level must be reported to the group team.
What ISA 600 (Revised) changed about component materiality
The previous version of ISA 600 used a classification model. Components were either "significant" (by financial significance or identified significant risk) or "not significant." Materiality allocation followed from the classification. A significant component received a full-scope audit with component materiality set by the group engagement team. Non-significant components received analytical procedures or nothing.
ISA 600 (Revised) replaces this with a risk-based approach. The concept of "significant component" has been removed entirely. Instead, the group engagement team identifies and assesses risks of material misstatement at the group financial statement level first, then determines what work is needed at each component to respond to those assessed risks. The scoping decision is driven by risk, not by whether a component crosses a percentage threshold.
For materiality, the practical effect is that the group engagement team must now determine component performance materiality for every component where audit procedures will be performed on disaggregated financial information (ISA 600 (Revised) para. 30). Under the old standard, a non-significant component subjected only to analytical procedures did not receive a formal component materiality. Under the revised standard, if audit procedures are performed at the component level, component performance materiality must be determined.
Aggregation risk: the concept that drives the calculation
Aggregation risk is the probability that the aggregate of individually immaterial uncorrected and undetected misstatements across components exceeds group materiality. ISA 600 (Revised) para. A78 explains that component performance materiality is set to reduce aggregation risk to an appropriately low level.
The concept is not new (it existed implicitly in the previous standard), but ISA 600 (Revised) makes it explicit. The more components a group has, the higher the aggregation risk, because each component can harbour a misstatement just below its own materiality threshold.
Consider a group with ten components, each allocated component materiality equal to group materiality. Each component could have an undetected misstatement of, say, 90% of group materiality. Ten such misstatements aggregate to nine times group materiality. The group financial statements would be massively misstated while every individual component file shows a clean result.
The fix is mechanical: set component materiality lower than group materiality. How much lower depends on the number of components, the degree to which the group's financial information is disaggregated across them, and the assessed risk at each component. ISA 600 (Revised) does not prescribe a formula. It requires professional judgment. But the judgment must be documented and the reasoning must be traceable.
How to calculate component materiality in practice
ISA 600 (Revised) does not specify a calculation method. In practice, most mid-tier firms use a percentage of group materiality, adjusted for the number of components and their risk profiles. The common range is 60–85% of group materiality per component, with 75% being the most frequently applied starting point.
The percentage approach works like this. Start with group materiality (set under ISA 320 using the appropriate benchmark). Apply a component materiality percentage. The percentage is lower when there are more components (more aggregation risk) and higher when there are fewer components. Then set component performance materiality below component materiality, using the same approach as at the group level (typically 50–75% of component materiality).
| Number of components | Typical range | Rationale |
|---|---|---|
| 2–4 components | 75–85% of group materiality | Lower aggregation risk with fewer components |
| 5–10 components | 60–75% of group materiality | Moderate aggregation risk |
| More than 10 components | 50–65% of group materiality | Higher aggregation risk with many components |
An alternative approach (used by some firms) is the allocation method: divide group materiality across components based on their relative size, then apply a factor. For example, if a component represents 40% of group revenue, it receives 40% of group materiality, plus a buffer. This approach has a theoretical basis but creates practical problems when components are very unequal in size (a small component can receive a materiality so low that the audit becomes disproportionately expensive relative to the risk).
The percentage approach is simpler, more commonly applied, and easier to document. The ciferi materiality calculator supports both methods.
When to differentiate materiality across components
Not every component in a group carries the same risk. ISA 600 (Revised) para. A79 acknowledges that the group engagement team may determine different component performance materiality amounts for different components.
Reasons to set a lower component materiality for a specific component:
- The component has a significant risk identified at the group level (for example, a subsidiary with a complex revenue recognition arrangement).
- The component operates in a jurisdiction with a higher risk of fraud or non-compliance.
- The component has a history of misstatements identified in prior years.
- The component is being audited by a component auditor whose work the group engagement team has less ability to direct and supervise.
Reasons to set a higher component materiality (closer to group materiality):
- The component is small relative to the group.
- The component's financial information is straightforward (for example, a dormant holding entity).
- The component is audited directly by the group engagement team with full access to all records.
Documentation requirement
If different components receive different materiality amounts, the file must explain the differentiation. A flat percentage across all components is easy to document but may not reflect the actual risk profile. Differentiated percentages require more judgment and more documentation, but they produce a more defensible file.
The clearly trivial threshold at component level
ISA 600 (Revised) para. 30(b) requires the group engagement team to determine the threshold above which misstatements identified in the component financial information must be communicated to the group engagement team. This is the component-level equivalent of the "clearly trivial" threshold under ISA 450.
In practice, this threshold is set at a percentage of component materiality (typically 5%, consistent with the group-level approach under ISA 450.A2). Any misstatement at the component level above this threshold must be reported to the group engagement team for inclusion in the group schedule of uncorrected misstatements.
Inspector focus area
The European Common Audit Inspection Methodology specifically checks whether the group engagement team has documented the basis for determining both the component performance materiality and the communication threshold. If the file contains a component materiality figure but no documented rationale for the communication threshold, inspectors will flag it.
Worked example: Bakker Industrial B.V. group
Group profile: Bakker Industrial B.V. is a Dutch manufacturing holding company. The group consists of the parent entity and four wholly-owned subsidiaries: Bakker Machining B.V. (€32M revenue), Bakker Coatings B.V. (€18M revenue), Bakker GmbH (€12M revenue, German subsidiary), and Bakker Properties B.V. (€2M rental income, dormant investment property entity). Consolidated group revenue: €64M. Reporting framework: Dutch GAAP. All components audited by the group engagement team (no component auditors).
Step 1: Set group materiality
Group materiality: €480,000 (0.75% of €64M consolidated revenue). Group performance materiality: €360,000 (75% of group materiality). Group clearly trivial threshold: €24,000 (5% of group materiality).
Documentation note
Record the benchmark (revenue), the percentage (0.75%), and the rationale (profit fluctuates between years; revenue is stable). Cross-reference to the ISA 320 materiality working paper.
Step 2: Determine component performance materiality
Four components. Moderate aggregation risk (four is a manageable number but two of the operating subsidiaries are individually material to the group). Starting point: 75% of group materiality.
| Component | Revenue | % of group | Component PM | % of group materiality | Rationale |
|---|---|---|---|---|---|
| Bakker Machining B.V. | €32M | 50% | €340,000 | 71% | Largest subsidiary, significant revenue recognition risk (long-term contracts with percentage-of-completion). Set below 75% starting point. |
| Bakker Coatings B.V. | €18M | 28% | €360,000 | 75% | Standard risk profile, no individually significant risks beyond group-level risks. |
| Bakker GmbH | €12M | 19% | €310,000 | 65% | Different jurisdiction (Germany, HGB converted to Dutch GAAP), creating conversion risk. Less direct familiarity with German regulatory requirements. |
| Bakker Properties B.V. | €2M | 3% | €400,000 | 83% | Dormant property holding company, minimal transactions. Higher allocation prevents disproportionate audit effort on immaterial, low-risk entity. |
Aggregation risk assessment
The sum of maximum possible undetected misstatements (one per component, each just below component performance materiality) is €1,410,000. This exceeds group materiality of €480,000, which is expected. The mitigation is that the probability of every component having an undetected misstatement at the maximum level simultaneously is low. Document this assessment.
Step 3: Set communication thresholds
Each component's communication threshold: 5% of the respective component performance materiality.
- Bakker Machining: €17,000
- Bakker Coatings: €18,000
- Bakker GmbH: €15,500
- Bakker Properties: €20,000
Any misstatement above these thresholds at the component level is communicated to the group engagement team for the group schedule of uncorrected misstatements.
Step 4: Document and communicate
The group planning memorandum includes a component materiality table showing: component name, component revenue, percentage of group, component performance materiality amount, percentage of group materiality, and the communication threshold. This table is the single working paper that a reviewer needs to evaluate the allocation.
Documentation note
Cross-reference the component materiality table to the group ISA 320 working paper and the group audit instructions. If any component materiality is revised during fieldwork (for example, because a risk assessment changes), document the revision and the reason per ISA 600 (Revised) para. A80.
Practical checklist for component materiality
- Set group materiality first, using ISA 320. Component materiality is derived from group materiality, not calculated independently (ISA 600 (Revised) para. 30).
- Assess aggregation risk before choosing a percentage. Count the components where audit procedures will be performed on disaggregated information. More components means more aggregation risk means a lower percentage.
- Apply a starting percentage (75% is the most common mid-tier default) and adjust for each component's risk profile. Document the adjustment rationale for any component that deviates from the starting point.
- Set component performance materiality below component materiality (50–75% of component materiality is standard practice, consistent with the group-level ISA 320 approach).
- Set the communication threshold at 5% of component performance materiality. Include this threshold in the group audit instructions to each team member or component auditor.
- Produce a single summary table in the group planning memorandum showing all components, their materiality allocations, and the communication thresholds. This is the working paper reviewers check first.
Common mistakes inspectors flag
- The European Common Audit Inspection Methodology specifically evaluates whether the group engagement team documented the basis for determining component performance materiality and the communication threshold. Files where component materiality equals group materiality (no reduction for aggregation risk) are a finding under ISA 600 (Revised) para. 30.
- The FRC's 2022–23 inspection cycle identified group audit files where the group engagement team set a single flat component materiality across all components without considering the different risk profiles. ISA 600 (Revised) para. A79 permits but does not require differentiation. If the auditor chooses not to differentiate, the file should document why a uniform allocation is appropriate for this specific group.
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Frequently asked questions
What is aggregation risk in a group audit?
Aggregation risk is the probability that the aggregate of individually immaterial uncorrected and undetected misstatements across components exceeds group materiality. ISA 600 (Revised) para. A78 explains that component performance materiality is set to reduce aggregation risk to an appropriately low level. The more components a group has, the higher the aggregation risk, because each component can harbour a misstatement just below its own materiality threshold.
What percentage of group materiality should be used for component materiality?
ISA 600 (Revised) does not specify a percentage. In practice, most mid-tier firms use 60–85% of group materiality per component, with 75% being the most common starting point. For groups with two to four components, 75–85% is typical. For five to ten components, 60–75%. For more than ten components, 50–65%. These are starting points requiring professional judgment and documentation of why the chosen percentage is appropriate.
Can different components have different materiality levels?
Yes. ISA 600 (Revised) para. A79 acknowledges that the group engagement team may determine different component performance materiality amounts for different components. Reasons to set a lower amount include significant risks at the component level, higher-risk jurisdictions, or a history of misstatements. Reasons to set a higher amount include the component being small, low-risk, or dormant. If different components receive different amounts, the file must explain the differentiation.
What changed about component materiality in ISA 600 (Revised)?
The previous ISA 600 used a classification model where components were either "significant" or "not significant." ISA 600 (Revised), effective for periods beginning on or after 15 December 2023, replaces this with a risk-based approach. The concept of "significant component" has been removed entirely. The group engagement team must now determine component performance materiality for every component where audit procedures are performed on disaggregated financial information (ISA 600 (Revised) para. 30).
What is the communication threshold at component level?
ISA 600 (Revised) para. 30(b) requires the group engagement team to determine the threshold above which misstatements identified in the component financial information must be communicated to the group engagement team. In practice, this is set at 5% of component performance materiality, consistent with the group-level "clearly trivial" threshold under ISA 450.A2. Any misstatement above this threshold at the component level must be reported for the group schedule of uncorrected misstatements.
Further reading and source references
- IAASB Handbook 2024: the authoritative source for ISA 600 (Revised), including the application material on component performance materiality (paras. A78–A80).
- ISA 320, Materiality in Planning and Performing an Audit: group materiality is set under ISA 320 before component materiality is determined.
- ISA 450, Evaluation of Misstatements Identified during the Audit: the "clearly trivial" threshold concept that informs the component communication threshold.
- ICAS Implementation Guidance on ISA 600 (Revised): practical guidance on the transition from the "significant component" model to the risk-based approach.
- European Common Audit Inspection Methodology: the inspection framework that specifically evaluates component materiality documentation in group audit files.