Standard: ISSA 5000, General Requirements for Sustainability Assurance Engagements · Issued: November 2024 · Publisher: IAASB / IFAC · Last reviewed: August 2026 ·  Jeremiah Say Lead Systems Architect Builds the calculation engines and methodology documentation behind GreenCalculus.com. Every position on this page is taken from the IAASB’s own staff publications on ISSA 5000 rather than from commentary about them. LinkedIn GitHub Full profile →  ·  GreenCalculus Engineering Verification function Checks that an assurance standard is never described as imposing a reporting duty, that a standard which survives is not described as withdrawn, and that every requirement stated here appears in the IAASB’s published material. How we verify →

ISSA 5000 — The Standard Behind Every Sustainability Assurance Report

ISSA 5000 is effective for periods beginning on or after 15 December 2026. It covers assurance over all sustainability information on any topic under any suitable criteria, is profession-agnostic subject to the IESBA Code and ISQM 1, supports limited and reasonable assurance, and is stand-alone — no other IAASB standard has to be applied.
MB v2026.203 · updated 22 Sep 2026
Standard ISSA 5000, General Requirements for Sustainability Assurance Engagements
Issued by International Auditing and Assurance Standards Board, November 2024
Effective Periods beginning on or after 15 December 2026, or information as at a specific date on or after that day
Scope All assurance engagements on sustainability information, any topic, any suitable criteria, any entity type or size
Who may apply it Any assurance practitioner complying with the IESBA Code and belonging to a firm applying ISQM 1, or requirements determined to be at least as demanding
GC stack layer Layer 6 — Assurance

ISSA 5000 is the standard that will sit behind almost every sustainability assurance report issued from 2027 onwards. It was published by the IAASB in November 2024, and it does something none of its predecessors attempted: it covers assurance over all sustainability information — climate, nature, human rights, labour practices, whatever a framework asks for — reported under any suitable criteria, by any qualifying practitioner.

It replaces a landscape of specialist standards with one general one. ISAE 3410, written for greenhouse gas statements, is withdrawn on the day ISSA 5000 takes effect. That transition — and the arithmetic of which reporting period falls under which standard — is covered on that page. This page is about what ISSA 5000 actually requires.

1. What ISSA 5000 is

It is an assurance standard: a set of requirements for the practitioner who examines sustainability information and expresses a conclusion on it. The purpose, in the IAASB’s terms, is for the practitioner to obtain sufficient appropriate evidence to express a conclusion designed to enhance the confidence of intended users that the information is relevant and reliable.

Three design decisions define it, and each is a departure from what came before.

SCOPE Every subject matter It applies across sustainability topics — climate, biodiversity, human rights, labour practices — and across aspects of them: risks and opportunities, governance, metrics, targets. One standard instead of many
CRITERIA Framework neutral It is written to work with any suitable reporting criteria, so a report prepared under IFRS S1 and S2, ESRS, GRI or a voluntary framework can all be assured under the same standard. The framework is the entity’s choice
PRACTITIONER Profession-agnostic Written to be used by professional accountants and non-accountant assurance practitioners alike, subject to two conditions that do most of the work. See §10

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2. It is not a reporting standard

This is the misunderstanding worth clearing first, because it is common and it inverts the standard’s purpose. ISSA 5000 requires no disclosure of anything by anyone. The IAASB is explicit:

“Preparing and reporting sustainability information is the responsibility of an entity’s management in accordance with a sustainability framework or standards or other suitable criteria. ISSA 5000 is applied by an assurance practitioner in undertaking an assurance engagement on sustainability information.” IAASB Staff, ISSA 5000 FAQ, January 2025

It was deliberately built so that an entity continues to decide what information is decision-relevant to its stakeholders. Nothing in it tells you to report a Scope 3 category, a biodiversity metric or a transition plan. Those duties come from ESRS, IFRS S2, a regulator or a stakeholder — and ISSA 5000 governs only the assurance of whatever results.

3. When it applies

ISSA 5000 is effective for assurance engagements on sustainability information reported for periods beginning on or after 15 December 2026, or reported as at a specific date on or after that day.

The date is about the reporting period, not the engagement

This catches people out. It is not “engagements starting after December 2026”. For a calendar-year reporter the first period squarely inside ISSA 5000 is FY2027, assured during 2028 — a full reporting cycle later than the headline date suggests. The corollary is a transition window for earlier periods, which is set out in full on the ISAE 3410 page rather than repeated here.

Whether assurance is required at all is a separate question, and not one the IAASB answers. Its standards are adopted at jurisdictional level, and each jurisdiction decides whether sustainability reporting and assurance are mandatory, for which entities, and who may perform the work.

4. Suitable criteria — the precondition most likely to bite

An assurance engagement cannot proceed unless its preconditions are present, and the one that fails most often is the criteria. The entity must have used suitable criteria to prepare the information. The IAASB defines those as criteria that result in sustainability information which is:

AttributeWhat it asks of the information
RelevantIt bears on the decisions the intended users are making.
CompleteNothing is omitted that would change how a user reads it.
ReliableIt can be measured or evaluated consistently by another competent practitioner.
NeutralIt is free from bias in what it presents and how.
UnderstandableA user can follow what it says without specialist reconstruction.

An established framework from an authorised or recognised body will normally satisfy this — IFRS S1 and S2 do, and the ISSB was consulted during development specifically to ensure compatibility. A bespoke internal methodology may not, and that is where engagements stall: not on the numbers, but on whether the basis for producing them is capable of being assured at all.

The second precondition is equally practical: the practitioner must expect to be able to obtain the evidence needed to support the conclusion. Where information cannot be evidenced — commonly deep in a value chain — that expectation may not hold.

5. Limited and reasonable assurance, in one standard

ISSA 5000 provides for both levels, and the distinction is not a matter of thoroughness alone. It changes the form of the conclusion you receive.

 Limited assuranceReasonable assurance
The conclusionWhether anything has come to the practitioner’s attention causing them to believe the information is not prepared, in all material respects, in accordance with the criteriaAn opinion on whether the information is prepared, in all material respects, in accordance with the criteria
Level obtainedSubstantially lower — but still meaningful to usersHigh, though never absolute
ProceduresVary in nature and timing from, and are less in extent than, reasonable assuranceMore extensive in nature, timing and extent
Financial-reporting analogueA review of financial statementsAn audit of financial statements
A majority of jurisdictions moving to mandatory sustainability assurance are starting with limited assurance and plan to transition to reasonable over time. IAASB Staff, ISSA 5000 FAQ, January 2025

That phasing matters for how a limited conclusion should be read. It is not a weaker version of an audit opinion; it is a differently shaped statement. And because most investors are accustomed to audited financial statements, some will expect the confidence of reasonable assurance from a report that does not provide it.

6. The engagement, end to end

The IAASB’s Implementation Guide organises an ISSA 5000 engagement into eight parts. They are worth knowing as a client, because they tell you when in the process you will be asked for what.

1 Fundamental principles and conceptsLimited and reasonable assurance, quality management, evidence and materiality — the ideas the rest of the engagement is built on.
2 Acceptance and continuanceIncluding the preconditions in §4. This is where an engagement is declined, and declining is a real outcome.
3 Group engagements, value chain, and using the work of othersThe part with no financial-audit equivalent at this scale — see §7.
4 PlanningOverall strategy, the engagement plan, and materiality.
5 Risk identification and assessmentWhere the information is most likely to be materially misstated. In practice: the estimated, the modelled and the newly measured.
6 Responding to the risksOverall responses plus procedures designed at the disclosure and assertion level.
7 ConcludingEvaluating whether the evidence is sufficient and appropriate, and the effect of uncorrected misstatements.
8 ReportingForming the conclusion and the form and content of the assurance report.
Misstatements are broader than wrong numbers

The standard treats a misstatement as qualitative or quantitative, and as including omitted information and information that obscures or misleads. A figure can be arithmetically correct and still be a misstatement if its presentation misleads. That is a wider test than most reporters expect, and it is the reason narrative disclosures are assurable at all.

7. Value chain, and using the work of others

The Implementation Guide gives the value chain a part of its own, alongside group engagements, and it is the structural difference between assuring sustainability information and assuring financial statements. A great deal of what an entity reports — Scope 3 above all — describes activity it does not control and data it did not produce.

Two consequences follow for anyone preparing for an engagement.

  • Evidence has to be obtainable, not merely asserted. The precondition in §4 requires the practitioner to expect they can obtain evidence supporting the conclusion. Value-chain data that cannot be evidenced puts that expectation under strain before the engagement begins.
  • Using someone else’s work is governed, not assumed. Where the practitioner relies on the work of others, ISSA 5000 addresses how — a supplier’s own assurance, a scheme certificate or a data provider’s figure is not automatically evidence in your engagement.

Our Emission Factor Gap Register and spend-based methodology deal with the same problem from the reporting side: where a value-chain figure comes from, and how much weight it can carry.

8. Materiality, including double materiality

Materiality in an assurance engagement has two sides that are easy to conflate. The entity applies materiality in deciding what to report; the practitioner applies it in planning and performing the engagement and in evaluating misstatements. ISSA 5000 addresses both, and the Implementation Guide devotes attention to the relationship.

The standard is written to accommodate frameworks that use double materiality — where an entity considers both how sustainability matters affect it and how it affects the environment, society and the economy — as well as frameworks that do not. That is a necessary consequence of being framework neutral: ESRS applies double materiality, IFRS S1 and S2 do not, and one assurance standard has to work over both.

The practitioner does not choose your materiality

A common expectation is that the assurer will decide what is material and test that. They do not. The entity’s management determines what is decision-relevant under its chosen criteria; the practitioner assesses whether the resulting information is materially misstated against those criteria. If your materiality process is undocumented, the engagement runs into that early — not because the practitioner disagrees with your conclusions, but because there is nothing to assess them against.

9. Who may perform an ISSA 5000 engagement

ISSA 5000 is profession-agnostic. Any assurance practitioner can use it, subject to two conditions — with a third route that is frequently left out of summaries.

1 The IESBA Code Compliance with the International Code of Ethics for Professional Accountants, including the International Independence Standards relating to sustainability assurance engagements.
2 ISQM 1 Membership of a firm that applies International Standard on Quality Management 1 — a designed, implemented and operating system of quality management covering sustainability engagements.
3 Or an equivalent regime Professional requirements, or requirements in law or regulation, that an appropriate authority has determined to be at least as demanding as the IESBA Code and ISQM 1.

The third route is what makes profession-agnosticism real rather than nominal. Without it, only firms already inside the accountancy infrastructure could qualify. With it, a jurisdiction can recognise an equivalent regime for engineering, certification or verification bodies — and those bodies can perform ISSA 5000 engagements.

Jurisdictions retain the final say. Law, regulation or local professional requirements may impose further limits on who may perform sustainability assurance in a particular market.

10. Stand-alone: no other IAASB standard required

ISSA 5000 does not require any other IAASB auditing or assurance standard to be applied alongside it. This is a deliberate design choice with a specific purpose: practitioners unfamiliar with the ISAs or the ISAEs can use it effectively without first learning them.

It is the technical counterpart to profession-agnosticism. A standard that could only be applied by someone fluent in the international auditing standards would be open to non-accountants in principle and closed to them in practice.

11. What it replaces, and what survives

The transition is narrower than it is often described, and the distinction matters if you also buy non-sustainability assurance.

StandardWhat happens
ISAE 3410
GHG statements		 Withdrawn with effect from 15 December 2026. ISSA 5000 covers GHG information, so a separate standard was judged unnecessary.
ISAE 3000 (Revised)
Other than audits or reviews		 Survives — but no longer for sustainability. It continues to be used for assurance engagements other than audits or reviews of historical financial information or assurance engagements on sustainability information.
ISO 14064-3
ISO verification		 Unaffected — a different standard-setter entirely. An IAASB withdrawal reaches only IAASB pronouncements.
ISAE 3000 (Revised) is not withdrawn

This is the easy mistake, and it is worth stating plainly because a lot of commentary blurs it. Only ISAE 3410 is withdrawn. ISAE 3000 (Revised) remains a live standard for the many assurance engagements that are neither an audit nor a review of historical financial information nor about sustainability — it simply stops being the vehicle for sustainability work.

12. Adoption is a jurisdictional decision

The IAASB sets the standard; it does not require anyone to use it. Adoption and implementation happen at jurisdictional level, and policymakers, standard-setters and regulators in each market decide when ISSA 5000 is required, whether additional local requirements are needed, and who is allowed to conduct the engagements.

Two practical consequences. A jurisdiction may adopt on a different timetable from the international effective date — which is what creates the route described on the ISAE 3410 page for practitioners in markets that have not yet adopted. And even where no regulator mandates assurance, entities frequently obtain it anyway, because investors and capital providers ask for it.

13. Interaction with the frameworks you report under

FrameworkHow ISSA 5000 meets it
IFRS S1 and IFRS S2Confirmed by the IAASB as providing suitable criteria that can be assured under ISSA 5000. The ISSB was among the standard-setters consulted during development to ensure compatibility.
CSRD / ESRSAssurance covers the sustainability statement as a whole, which suits a general standard better than a GHG-specific one. European assurance standards are also under development and may take precedence locally.
GRIFramework neutrality means a GRI-based report can be assured under ISSA 5000 provided the criteria are suitable for the information reported.
GHG ProtocolThe criteria most GHG statements are prepared against. ISSA 5000 assures the statement; the GHG Protocol governs how it was built.
A voluntary or bespoke frameworkAssurable only if the criteria are suitable — relevant, complete, reliable, neutral and understandable. This is where bespoke methodologies fail. See §4.

14. What this means for your emission factors

Nothing in ISSA 5000 imposes a factor-provenance test on the practitioner — the same position as under ISAE 3410 and ISO 14064-3. What changes is the surface area: a standard covering all sustainability information across a value chain asks the evidence question about far more of your reporting than a GHG-only standard did.

The engagement asks what you held when you published. The useful answer is one recorded at the time, not reconstructed afterwards.

Every factor in the MasterBrain carries its edition, publication and retrieval provenance, and historical values stay addressable by version, so that question has an answer that predates the engagement. Our Assurance Readiness Checker tests the gap between what the assurer examines and what remains your duty to hold.

15. Frequently Asked Questions

ISSA 5000, General Requirements for Sustainability Assurance Engagements, is the IAASB’s standard for assurance over sustainability information. Issued in November 2024, it applies to all assurance engagements on sustainability information — any topic, any suitable reporting criteria, any type or size of entity — and supports both limited and reasonable assurance. It is effective for periods beginning on or after 15 December 2026.

No. It is an assurance standard, not a reporting standard, and it imposes no disclosure requirement on any entity. Preparing and reporting sustainability information is management’s responsibility under whatever framework or criteria apply. ISSA 5000 governs only the work of the practitioner who assures that information.

Periods beginning on or after 15 December 2026, or information as at a specific date on or after that day. The test is the reporting period, not the date the engagement is accepted — so for a calendar-year reporter the first period squarely inside ISSA 5000 is FY2027, assured during 2028. Earlier periods sit in a transition window covered on our ISAE 3410 page.

Yes. The standard is deliberately profession-agnostic. The practitioner must comply with the IESBA Code including its independence requirements, and belong to a firm that applies ISQM 1 — or follow professional requirements, or requirements in law or regulation, that an appropriate authority has determined to be at least as demanding as those two. That third route is what makes the standard genuinely open beyond the accountancy profession. Local law may still restrict who can perform the work in a given market.

Yes. The IAASB confirms that S1 and S2 are among the frameworks providing suitable criteria that can be assured under ISSA 5000, and the ISSB was one of the standard-setters consulted during its development to ensure compatibility. The standard is framework neutral, so it works with any criteria that are suitable — meaning they produce information that is relevant, complete, reliable, neutral and understandable.

No. ISSA 5000 is a stand-alone standard and does not require any other IAASB auditing or assurance standard to be applied. That is deliberate: it allows practitioners who are not familiar with the ISAs or ISAEs to use it effectively. The exceptions are the ethical and quality-management requirements — the IESBA Code and ISQM 1, or an equivalent regime — which are conditions of using it at all.

No — only ISAE 3410 is withdrawn. ISAE 3000 (Revised) continues to be used for assurance engagements other than audits or reviews of historical financial information or assurance engagements on sustainability information. In other words it survives as a standard, but stops being the vehicle for sustainability assurance once ISSA 5000 is effective.

It depends who is reading. A limited assurance conclusion states whether anything came to the practitioner’s attention causing them to believe the information is not prepared in accordance with the criteria — a different shape of statement from an opinion, on substantially less work. A majority of jurisdictions moving to mandatory assurance are starting with limited and plan to move to reasonable over time, but some investors accustomed to audited financial statements will expect the higher level sooner.

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How to cite this page. GreenCalculus (2026). ISSA 5000 — The Standard Behind Every Sustainability Assurance Report. Reviewed 31 August 2026. Positions are taken from the IAASB staff publication Frequently Asked Questions: International Standard on Sustainability Assurance 5000 (January 2025) and ISSA 5000 FAQ — Applicability of ISSA 5000, ISAE 3000 (Revised) and ISAE 3410 (August 2025), together with ISSA 5000 itself, issued November 2024. This page describes a standard. It is not professional advice, and whether and how ISSA 5000 applies to a particular engagement is a matter for your jurisdiction and your assurance provider.

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