In ESG assurance, materiality decides two things: which sustainability topics belong in your report, and how much error a practitioner will tolerate in the numbers and statements about them. The first is a reporting judgment made by the company. The second is an assurance judgment made by the practitioner, using the first as its starting point. If the topic selection is weak, the assurance engagement inherits the weakness. This guide explains how the two connect, how the main definitions differ, and what to prepare before an assurance provider arrives.
TL;DR
- Materiality in sustainability reporting is user-driven: information is material if omitting or misstating it could reasonably influence the decisions of intended users.
- Financial materiality looks at effects on the entity; impact materiality looks at the entity's effects on people and the environment; double materiality applies both lenses.
- In assurance, materiality guides risk assessment, the evidence you must gather, and how misstatements are evaluated, often with separate treatment of qualitative and quantitative disclosures.
- Frameworks such as ESRS do not prescribe one assessment process, so a documented, transparent method that an assurance provider can follow is your best protection.
- Practitioners who understand both sides of the line are the ones who make assurance engagements run smoothly.
Table of Contents
- What materiality means in ESG reporting and assurance
- Financial, impact and double materiality
- How companies identify and prioritize material topics
- How materiality changes the way assurance is planned
- What to prepare before the assurance provider arrives
- Where ISSA 5000 fits
- Our perspective
- Build the competence behind the assessment
- FAQ
- Sources
What materiality means in ESG reporting and assurance
Materiality in sustainability reporting is a user-driven concept. It rests on the common information needs of the intended users of the report, and information is material if its omission or misstatement could reasonably be expected to influence the decisions those users make based on the sustainability information. That is the framing the IAASB's 2023 FAQ on ISSA 5000 materiality uses, and it is the one assurance practitioners work from.
Two points follow from that definition.
First, materiality is not a property of a topic in the abstract. It depends on who is reading and what they decide. An investor deciding on capital allocation, a regulator, an employee representative and a community group may each need different information.
Second, the word is used at two levels. At the reporting level, a company decides which topics and metrics to disclose. At the assurance level, a practitioner decides what size of misstatement would matter and plans work accordingly. Mixing the two is the most common source of confusion when finance teams first meet sustainability assurance.
Financial, impact and double materiality
The vocabulary differs by framework, but three concepts cover most of the ground.
| Concept | The question it asks | Typical focus |
|---|---|---|
| Financial materiality | Does this matter create risks or opportunities that could affect the entity's finances? | Financial performance, position, cash flows, cost of capital |
| Impact materiality | What effect does the entity have on people and the environment? | Actual or potential, positive or negative impacts |
| Double materiality | Does the matter meet either test? | Both lenses combined |
Financial materiality. The EPRA materiality assessment guidance describes it as assessing whether a sustainability matter generates risks or opportunities expected to have a material influence on an entity's financial performance, position, cash flows or cost of capital. This is the outside-in view: how the world affects the company.
Impact materiality. Under the version of ESRS 1 that EFRAG published in December 2025, impact materiality evaluates the entity's material actual or potential, positive or negative impacts on people or the environment over the short, medium or long term, across operations, value chains and business relationships. This is the inside-out view.
Double materiality. A topic is reported if it passes either test. Our walkthrough of the double materiality assessment under ESRS covers the mechanics in more detail.
A practical consequence: a topic can be immaterial financially and still be reportable because of the harm the company causes. Teams trained only in financial reporting often discard such topics too early.
How companies identify and prioritize material topics
There is no single mandated procedure. The EFRAG implementation guidance on materiality assessment says ESRS leaves the exact steps to the undertaking's judgment while expecting transparency about how it was done. A typical sequence, as the same guidance describes it, starts with understanding context, engages stakeholders, assesses impacts through the inside-out lens, and then evaluates financial implications.
In practice, most teams build a method along these lines:
- Map context. Operations, value chain, business relationships, geographies and sector.
- Build a long list. Topics drawn from the standards, sector peers, and internal risk registers.
- Engage stakeholders. Affected groups and report users, with a record of who was consulted and why.
- Score impacts. Severity and likelihood are the criteria ESRS provides for impacts.
- Score financial effects. Magnitude and likelihood of risks and opportunities.
- Set thresholds and decide. Define in advance what score makes a topic material, then apply it consistently.
- Document and approve. Keep the reasoning, the data and the governance sign-off together.
Judgment is unavoidable
A 2022 Berkeley article by Garst, Maas and Suijs calls materiality assessment both an art and a science, because sustainability issues carry inherent uncertainty. The authors also argue that assessments should not focus only on win-win topics. They should include tensioned topics that carry significant societal impact without a clear business case.
The ICAS report on materiality assessments takes a related view: companies should define material topics starting from impact materiality, then assess them through a financial lens. Whether you follow that order or not, write down why you chose it.
There is also a legal dimension. A 2024 academic article by Félix E. Mezzanotte notes that early implementation of mandatory impact materiality rules may expose companies to increased legal risk. A defensible, documented process is therefore protection as well as good practice.
How materiality changes the way assurance is planned
Once the report exists, the practitioner applies materiality again. The ISSA 5000 implementation guide explains that materiality dictates the scope and depth of the engagement by guiding strategy, risk assessment and procedures. The practitioner must distinguish between qualitative and quantitative disclosures and determine appropriate thresholds to judge whether the information is free from material misstatement.
The IAASB's FAQ adds detail on how this plays out. Practitioners apply materiality to:
- design risk assessment procedures,
- determine what evidence to gather, and
- evaluate misstatements found.
They often use a bifurcated approach, treating qualitative and quantitative disclosures differently. A greenhouse gas total can carry a numerical threshold. A statement about a governance process or a transition plan is judged by whether a misdescription would mislead users, and no percentage fits it.
When two materiality lenses apply
Where both financial and impact materiality apply, the same FAQ notes that practitioners usually use the lesser of the two thresholds for quantitative disclosures, so that the information needs of both user groups are met. For a reporting team, this has a plain implication: a double materiality report can be tested to a tighter tolerance than a single-lens report with the same figures.
Forward-looking and complex information
For ESG metrics assured under ISAE 3000 (Revised), the ICAEW guidance on assurance opinions on ESG metrics asks practitioners to consider the complexity of the subject matter, the effect of forward-looking information and the needs of a broad stakeholder group. Targets, scenario analysis and transition plans therefore need especially careful support, since there is no historical ledger behind them.
What to prepare before the assurance provider arrives
The EFRAG guidance does not prescribe specific documentation, but it advises producing documentation suitable for audit and assurance providers. Read that as a standard of usefulness: could an independent person reconstruct your conclusions?
A workable file contains:
- Method statement. Criteria, scales, thresholds and the reasons they were chosen.
- Stakeholder record. Who was consulted, how, when, and what was done with their input.
- Topic log. Every topic considered, with the decision and rationale, including topics you excluded.
- Data lineage. For each material metric, the source systems, owners, calculation logic and controls.
- Governance trail. Review and approval by the people accountable, such as the board or audit committee.
- Change log. What differs from the last cycle and why.
The excluded-topics log is the item teams most often skip, and it is the one assurance practitioners ask about first. Once you publish claims based on your material topics, check that the wording holds up too; this EU environmental claims check is a useful lens for reviewing how those claims read on your website.
Common failure points
- A matrix built once and never refreshed when the business changes.
- Scoring criteria invented after seeing the results.
- Stakeholder engagement limited to the groups that are easiest to reach.
- Material topics in the narrative that have no metric, owner or control behind them.
- Thresholds that are undocumented, so the practitioner has to guess your tolerance.
Where ISSA 5000 fits
The ISSA 5000 implementation guide describes the standard as authoritative and practitioner-agnostic: it governs sustainability assurance engagements regardless of reporting framework or entity size. Practitioners must follow its requirements on quality management, ethical conduct and the application of materiality, and it provides the structure for obtaining evidence and evaluating misstatements across qualitative and quantitative disclosures. For a deeper look at the standard, read our overview of ISSA 5000, the new global sustainability assurance standard. For readiness steps, see sustainability reporting assurance: standards and readiness.
Our perspective
We see the same pattern in the teams we train. The materiality assessment gets treated as a communications exercise, a colorful matrix produced by the sustainability team. The assurance engagement then treats it as evidence, and the two do not match.
The fix is not more sophistication. It is traceability. Every material topic should lead to a metric, every metric to an owner and a control, and every exclusion to a written reason. When finance, sustainability and risk functions share one method, assurance becomes a review of something that already holds together, not a reconstruction.
We also believe practitioners on both sides need the same vocabulary. A preparer who understands how a practitioner sets thresholds writes better disclosures. A practitioner who understands how a double materiality assessment was built asks sharper questions. That shared competence is why our programs are mapped to ISSB, ESRS, GRI and ISSA 5000 and why our assessments have real pass thresholds rather than participation credit.
— Ransford
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FAQ
What is the difference between reporting materiality and assurance materiality?
Reporting materiality decides which topics and metrics a company discloses. Assurance materiality is the practitioner's threshold for how much misstatement would influence users, and it sets how much work is done. Both rest on the same user-driven definition, but the first is the company's judgment and the second is the practitioner's.
Does ESRS require a specific materiality assessment process?
No. According to EFRAG's implementation guidance, ESRS leaves the exact steps to the undertaking's judgment while expecting transparency. You need a method that is consistent, documented and explainable, because the assurance provider will test how you reached your conclusions.
Which threshold applies when a report uses both financial and impact materiality?
The IAASB's FAQ on ISSA 5000 notes that practitioners usually use the lesser of the two thresholds for quantitative disclosures. This ensures that the information needs behind both lenses are met. Qualitative disclosures are judged on whether a misstatement or omission could influence users.
What documentation will an assurance provider want to see?
No specific set is prescribed, but EFRAG advises documentation suitable for audit and assurance providers. In practice that means a method statement, stakeholder engagement records, a log of included and excluded topics, data lineage for material metrics, and evidence of governance approval.
Sources
- IAASB FAQ on ISSA 5000 materiality (October 2023)
- ISSA 5000 implementation guide
- EFRAG ESRS 1 (December 2025)
- EFRAG materiality assessment implementation guidance (May 2024)
- EPRA materiality assessment guidance (April 2024)
- Garst, Maas and Suijs, Materiality Assessment Is an Art, Not a Science (2022)
- ICAS report on materiality assessments (2024)
- Mezzanotte, corporate sustainability reporting and double materiality (2024)
- ICAEW, assurance opinions on ESG metrics under ISAE 3000 (Revised)
- EU environmental claims check