ISAE 3000 and ISAE 3410

What is ISAE 3000?

ISAE 3000 (Revised), Assurance Engagements Other than Audits or Reviews of Historical Financial Information, sets the requirements for any assurance engagement on subject matter other than historical financial information, such as sustainability reports, key performance indicators or compliance with rules. It requires the practitioner to check preconditions, including that the criteria are suitable and available to users; to plan and perform the work with professional scepticism; to apply materiality; to obtain evidence suited to limited or reasonable assurance; and to issue a report with a clear conclusion. It works with the IESBA Code of Ethics and quality management standards. See sustainability assurance explained.

What is ISAE 3410?

ISAE 3410, Assurance Engagements on Greenhouse Gas Statements, adds requirements specific to emissions: understanding the company's emissions sources, boundaries and quantification methods; assessing risks such as incomplete sources, wrong emission factors and errors in estimates; considering scientific uncertainty; and testing activity data, factors and calculations. It includes illustrative limited and reasonable assurance reports. It is always used with ISAE 3000. See calculating scope 1 and 2 emissions.

How does an ISAE 3000 or 3410 engagement work?

The practitioner agrees terms with the company, including the subject matter, criteria such as the GHG Protocol and the level of assurance; understands the company's processes and, for reasonable assurance, its controls; sets materiality, commonly around 5% for emissions totals; assesses risks; performs procedures such as analytical review, inquiries, recalculation and tests of source data; evaluates misstatements; and reports. A limited assurance report states that nothing has come to the practitioner's attention suggesting material misstatement; a reasonable assurance report gives a positive opinion. See limited and reasonable assurance.

ISAE 3000 and ISSA 5000: which standard for which period?

ISSA 5000 applies to sustainability information for periods beginning on or after 15 December 2026, and ISAE 3410 is withdrawn from the same date. The reporting period's start date decides the standard.

A company with a calendar year will have its 2026 report assured under ISAE 3000 and ISAE 3410, unless its provider applies ISSA 5000 early, and its 2027 report under ISSA 5000. A company with a year starting on 1 July moves a year later in practice, with its year to June 2027 still under the old standards. CARB's proposals for SB 253 accept ISAE 3000 with ISAE 3410 for engagements starting before 15 December 2026 and ISSA 5000 after. In Australia, ASAE 3410 continues for separate emissions reporting under national greenhouse laws until periods starting on 15 December 2026. Accredited verification bodies use a different standard, ISO 14064-3; see GHG verification. See ISSA 5000.

What happens to ISAE 3000 after ISSA 5000?

ISAE 3000 (Revised) remains in force for assurance on subject matters that are not sustainability information, such as compliance or some operational information. For sustainability information, including greenhouse gas statements, ISSA 5000 becomes the standard, and the IAASB has published guidance on moving from ISAE 3000 to ISSA 5000. Practitioners who already apply ISAE 3000 and ISAE 3410 will find much familiar in ISSA 5000, which was built on them but adds more detail on materiality, estimates, group engagements and value chain information.

How should readers interpret existing assurance reports?

Check the standard named, the level of assurance, the exact information covered, the criteria, any limitations or modified conclusions, and whether the practitioner is an audit firm or a specialist verifier. A limited assurance report under ISAE 3000 over selected metrics gives much less comfort than reasonable assurance over the full emissions inventory. See the CSRD after the Omnibus.

This guide is general information. It is not tax or legal advice for your situation.