Much has been written about sustainability materiality in recent years.
Entire methodologies have emerged to define it, regulators have refined its application, and assurance standards now devote considerable attention to evaluating it. Yet despite this growing sophistication, discussions around materiality often become circular and, at times, Sisyphean. Organisations spend months developing materiality assessments, only to revisit the same debates during Board approval, external assurance, or regulatory review.
This is often interpreted as evidence that materiality is inherently subjective and overly reliant on professional judgement. That is not the real issue. The recent ISSA 5000 FAQs suggest the conversation needs to shift from defining materiality to understanding the governance processes behind it.
The more fundamental problem is that materiality is still treated as a single judgement, when in reality it is a sequence of related judgements made by different participants within a governance system. Each participant asks a different question, applies a different evidential threshold, and ultimately makes a different decision. Labelling all these decisions as materiality has obscured rather than clarified the governance challenge.
The Role of the Reasonable Investor
The concept of the reasonable investor illustrates this clearly. It has a long history in securities law and has recently been revisited by Sharfman (2025). Within IFRS and AASB aligned sustainability reporting frameworks, materiality is intended to support decisions made by existing and potential investors, lenders, and other creditors (IFRS S1, para 18; AASB S2).
Other frameworks proceed from different starting points. GRI focuses on an organisation's most significant impacts on the economy, environment, and people, while the European ESRS adopts a double materiality approach. Under AASB S2, however, the financial materiality lens applies. Management therefore begins by asking whether information could reasonably influence those decisions.
This is only the first judgement in a much longer chain.
Materiality as a Governance Chain
The Board is not simply deciding whether a risk is material. It is deciding whether management's conclusion is one it is prepared to govern and endorse. The external assurer is not determining whether it agrees with management's assessment. It evaluates whether the framework has been applied appropriately, whether sufficient appropriate evidence supports the conclusion, and whether the information is free from material misstatement.
A regulator may then ask whether another reasonable entity, applying the same framework in comparable circumstances, would have reached a similar conclusion. In Australia, ASIC administers the regime and may review both sustainability reports and assurance files (ASIC, RG 280). Investors ultimately decide whether the disclosures are genuinely decision useful.
These are not interchangeable judgements. They are distinct governance responsibilities revolving around the same concept.
Viewed in this way, materiality is less an accounting threshold and more a governance architecture. Each participant performs a different function and is expected to challenge, not replicate, the conclusions before them. Testing is not the same as re-performing. The assurer is required to understand and evaluate management's process, not re-run the underlying assessment (ISSA 5000). The objective is not identical thinking at every stage, but reasoning that can withstand increasingly rigorous scrutiny.
Rethinking Consensus in Materiality Assessments
This has important implications for how organisations govern sustainability reporting. Materiality workshops are often designed to achieve consensus as efficiently as possible. While understandable, consensus may be the wrong objective.
Sustainability reporting requires judgements about uncertain future events, including evolving regulation, emerging technologies, physical climate risks, and changing investor expectations. In this context, disagreement is not a failure of governance. It is evidence that governance is functioning.
Immediate consensus on complex issues should create discomfort. Robust governance should surface competing interpretations, conflicting evidence, and alternative assumptions before arriving at a conclusion. The process resembles scientific peer review more than a vote. A judgement becomes more reliable because it has survived informed challenge.
Understanding the Role of Assurance
This perspective also clarifies the role of sustainability assurance under ISSA 5000. Assurance is often described as providing confidence over sustainability information, but this can be misleading. It suggests that the assurer is verifying whether management reached the correct conclusion, when the standard requires something more nuanced.
ISSA 5000 distinguishes between the entity's process for determining what to report and the practitioner's separate application of materiality in planning and performing the engagement (IAASB ISSA 5000 Materiality FAQ, Q2 and Q3). The assurer evaluates whether management's process is appropriate and whether the information system supports preparation in accordance with the framework. It does not re-perform the entity's materiality assessment.
This understanding informs the practitioner's risk assessment and supports a conclusion on whether the disclosures are free from material misstatement. The process itself is not the object of the opinion, but it shapes how the assurer reaches one.
Why Process Matters More Than Outcome
The implications of this distinction are significant. Two organisations may conclude that biodiversity is not currently material to their financial prospects and publish identical disclosures. One may have reached this conclusion through rigorous cross functional analysis, supported by external evidence and extensive Board challenge. The other may have reached the same conclusion through a brief internal workshop with limited analysis.
The reported outcome is identical. The confidence stakeholders should place in it is not.
The difference lies in the evidence. A rigorous process produces an evidential trail that can be tested. A weaker process does not. This is precisely the type of gap that a practitioner's risk assessment is designed to expose. Assurance derives much of its value not from re-deciding the final answer, but from determining whether disclosures are supported by sufficient appropriate evidence and are free from material misstatement (IAASB ISSA 5000 Materiality FAQ, Q9, Q12).
Materiality and Organisational Maturity
This also raises a broader question about organisational maturity. As sustainability reporting becomes embedded in business decision making, should different materiality judgements across an organisation begin to converge?
Today, it is common for a sustainability team to identify an issue as material for disclosure, while finance does not reflect it in impairment testing, strategy adjusts investment priorities, and treasury sees no impact on financing costs. Each judgement may be valid because each serves a different purpose and operates under a different evidential threshold.
Over time, these judgements should become more coherent. Disclosure materiality, strategic decision making, capital allocation, and financial reporting may not produce identical conclusions, but they should be able to explain their differences through a consistent chain of reasoning.
The distance between these judgements may be an overlooked indicator of reporting maturity. Organisations often assess maturity based on disclosure completeness or data sophistication. Equally important is whether sustainability information has become sufficiently reliable and decision useful that different governance functions can rely on it consistently.
Conclusion
The question has never simply been whether a sustainability issue is material. The more important question is how an organisation ensures that multiple participants, each with different responsibilities and standards of judgement, produce a coherent and evidence-based narrative that supports investor decision making.
Materiality is not a conclusion reached at the end of a workshop. It is the product of a governance system designed to transform uncertainty into defensible judgement.
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