Sustainability assurance standards reference
Scope of this page
What it covers. The assurance standards that apply to sustainability and climate reporting: the international standard, the two older standards still in use, and the national adoptions we have been able to verify against a primary source. 10 standards in total.
What it does not cover. Singapore, Malaysia, Japan, China, Turkiye, Brazil, Nigeria and the other jurisdictions in our adoption tracker are not listed above. That is because we have not yet read a primary source confirming which assurance standard applies there, not because none applies. Several of those jurisdictions do mandate assurance on a timetable, which is recorded in the assurance column of the adoption tracker.
How it is verified. Every row links to the standard-setter or regulator. Where a source does not state a field, the cell reads Not verified. 2 of 10 rows currently contain at least one unverified cell. Last verified 2026-08-12.
The standards
Scroll the table sideways to see every column →
| Body | Standard | Status | What it applies to | Assurance levels | Effective from | Mandatory? | Source |
|---|---|---|---|---|---|---|---|
| IAASB (international)# | ISSA 5000 General Requirements for Sustainability Assurance Engagements | Final | Any sustainability topic, any reporting framework, any assurance practitioner | Limited and reasonable | Periods beginning on or after 15 December 2026, or as at a specific date on or after that date. Early adoption encouraged. | Not itself a legal requirement. Becomes mandatory only where a jurisdiction adopts it. | IAASB |
| IAASB (international)# | ISAE 3000 (Revised) Assurance Engagements Other than Audits or Reviews of Historical Financial Information | Final, pre-existing | The general-purpose assurance standard. It is what most sustainability assurance has been performed under to date, in the absence of a dedicated standard. | Limited and reasonable | In force. Not withdrawn: it remains the standard for assurance engagements generally, but sustainability engagements move to ISSA 5000 as jurisdictions adopt it. | Applies where a jurisdiction has not adopted ISSA 5000. | IAASB standards |
| IAASB (international)# | ISAE 3410 Assurance Engagements on Greenhouse Gas Statements | Being withdrawn | Greenhouse gas statements specifically, not wider sustainability information. | Limited and reasonable | In force until 15 December 2026, when it is withdrawn. ISSA 5000 takes effect on the same date and covers greenhouse gas information within its wider scope. | Do not build a long-term assurance approach on this standard. It is going away. | IAASB withdrawal notice |
| Australia (AUASB)# | ASSA 5000 General Requirements for Sustainability Assurance Engagements | Final | Australian equivalent of ISSA 5000. Stand-alone standard covering all aspects of a sustainability assurance engagement. | Limited and reasonable | Sustainability information reported for periods beginning on or after 1 January 2025. | Yes, for sustainability reports required under the Corporations Act 2001. | AUASB |
| Australia (AUASB)# | ASSA 5010 Timeline for Audits and Reviews of Information in Sustainability Reports under the Corporations Act 2001 | Final | Not a general requirements standard. It sets how much of the sustainability report must be assured, and at what level, during the phase-in. | Specifies which parts are reviewed (limited) and which audited (reasonable) | Phase-in running from 1 January 2025 to 30 June 2030. | Yes, alongside ASSA 5000. | AUASB |
| Hong Kong SAR (HKICPA)# | HKSSA 5000 General Requirements for Sustainability Assurance Engagements | Final | Conforms with ISSA 5000. | Limited and reasonable | Periods beginning on or after 15 December 2026. Earlier application permitted. | Not verified whether assurance is yet mandated for HKFRS S2 reporters. The standard exists; the mandate is a separate question. | HKICPA |
| Canada (AASB Canada)# | CSSA 5000 General Requirements for Sustainability Assurance Engagements | Final | ISSA 5000 adopted with Canadian amendments to the effective date and to align with Canadian ethical requirements. Any sustainability topic, any framework. | Limited and reasonable | Periods beginning on or after 15 December 2027, or as at a specific date on or after that date. Note this is a year later than ISSA 5000. | Canada has no economy-wide mandatory sustainability assurance requirement. The standard governs engagements that are performed. | FRAS Canada |
| United Kingdom (FRC)# | ISSA (UK) 5000 General Requirements for Sustainability Assurance Engagements | Final | UK version of ISSA 5000, issued for voluntary use by UK assurance providers. | Limited and reasonable | Periods beginning on or after 15 December 2026. Early application permitted. | No. Explicitly issued for voluntary use. There is no UK statutory sustainability assurance mandate attached to it. | FRC |
| European Union# | CSRD limited assurance requirement, with CEAOB guidelines in the interim | Requirement in force, standard pending | Sustainability reporting under the CSRD and ESRS. | Limited assurance | The assurance requirement applies from the first CSRD reporting. The European Commission is required to adopt limited assurance standards by delegated act; that deadline is 1 July 2027. | Yes. The CSRD introduced an EU-wide requirement for limited assurance over sustainability reporting. | CEAOB guidelines |
| Philippines (AASC)# | PSSA 5000 General Requirements for Sustainability Assurance Engagements | Issued | Philippine adoption of ISSA 5000. | Limited and reasonable | Not verified | Not verified | IAASB adoption tracker |
Limited and reasonable assurance are not two grades of the same thing
They differ in the form of the conclusion, not merely in effort.
Limited assurance produces a conclusion in the negative form: nothing has come to the practitioner's attention causing them to believe the information is materially misstated. The practitioner does less work, and says less.
Reasonable assurance produces a positive opinion, in the same form as an audit opinion on financial statements. It requires substantially more evidence.
The practical consequence is that a limited assurance conclusion is not a weaker version of an opinion. It is a different statement. Reading it as "the report is correct, just less thoroughly checked" misreads what has been given.
What ISSA 5000 changed
Three things matter for a preparer rather than a practitioner.
It is framework-neutral. ISSA 5000 applies to sustainability information prepared under any reporting framework, not only the ISSB Standards. The same standard can be used for an ESRS engagement and an IFRS S2 engagement.
It is profession-agnostic. It is written to be used by any assurance practitioner, not only accountants. Whether a non-accountant may sign an assurance report in your jurisdiction is a separate question, set by that jurisdiction.
It covers both levels in one standard. Limited and reasonable assurance are dealt with together, with the requirements differentiated where they need to be, rather than in separate standards.
There is also a consequence worth planning around: ISAE 3410, the greenhouse gas assurance standard, is being withdrawn with effect from 15 December 2026, the date ISSA 5000 takes effect. Greenhouse gas information falls within the wider scope of ISSA 5000 instead. If your current assurance arrangements are built specifically around ISAE 3410, that is a change to plan for rather than to discover.
Reading the effective dates
The dates in the table are the dates the assurance standard applies to an engagement. They are not the dates you must obtain assurance. Those are set by whoever mandates assurance in your jurisdiction, and the two are frequently different.
Australia is the clearest case. ASSA 5000 applies from periods beginning on or after 1 January 2025, but how much of the report must be assured, and at what level, is set separately by ASSA 5010 across a phase-in running to 30 June 2030. Canada is the opposite case: the standard exists and is effective a year later than the international one, but nothing mandates its use economy-wide.
A jurisdiction can therefore have an assurance standard and no assurance requirement, or an assurance requirement and no locally adopted standard. The European Union is currently in the second position, which is why the CEAOB guidelines exist.
What assurance readiness actually asks of you
Assurance is an evidence exercise. A practitioner has to be able to test how a number was produced, not only what it is. In practice that means being able to show, for each disclosed figure, where the data came from, what was done to it, who approved it and when, and what changed between versions.
That is a records problem before it is a reporting problem, and it is the reason first-cycle assurance findings tend to concentrate on process rather than on the numbers themselves. You can see what an append-only, timestamped record of that kind behaves like on our public tamper demo, which is open and requires no account.
Related references
For which jurisdictions require assurance and from when, see the assurance column of IFRS S2 adoption by jurisdiction. For the terms used above, see the IFRS S2 terminology reference. For how the disclosure requirements map across regimes, see the IFRS S2, ESRS and TCFD crosswalk.
How to cite this page
Auditably Research. "Sustainability assurance standards reference." Auditably.
https://auditably.co/blog/sustainability-assurance-standards-reference (accessed [date]).
If your jurisdiction is missing or a row is out of date, email [email protected] with the primary source and it will be checked and added.