Auditors and other professional assurance practitioners will want to become familiar with the new general-purpose standard for sustainability assurance.
The new International Standard on Sustainability Assurance (ISSA) 5000, General Requirements for Sustainability Assurance Engagements and Conforming and Consequential Amendments to Other IAASB Standards Arising from ISSA 5000, has been published by the International Auditing and Assurance Standards Board (IAASB).
ISSA 5000 is effective for assurance engagements on sustainability information reported for periods beginning on or after 15 December 2026, or as at a specific date on or after 15 December 2026. Early application is permitted.
“We are at the advent of a new era of external reporting. Users will expect a broader range of information — financial and non-financial information — to assess corporate performance,” said Tom Seidenstein, Chair of the IAASB, in a keynote address on shaping the future of sustainability assurance engagements.
With ISSA 5000, the IAASB aims to create a global baseline that can work in every jurisdiction for a wide range of engagements by a diversity of practitioners.
The principles-based standalone ISSA 5000:
- is suitable for any sustainability assurance engagement;
- can be applied to sustainability information reported across any sustainability topic and prepared under multiple frameworks;
- supports the application of traditional financial materiality and ‘double materiality’ that unites financial materiality and impact materiality;
- deals with reasonable and limited assurance engagements and differences in the associated work effort;
- supports use by professional accountant and non-accountant assurance practitioners; and
- includes guidance on application and other explanatory material.
“In developing ISSA 5000, we were mindful of the practical challenges of implementation,” said Seidenstein. “We built off existing practices already embedded in our well-established and widely used assurance standards,” he said, citing ISAE 3000 (for non-sustainability assurance) and ISAE 3410 (for greenhouse gas statements). “We also paid particular attention to scalability and proportionality throughout.”
We are at the advent of a new era of external reporting
Seidenstein noted that although elements of ISSA 5000 – such as support for double materiality and limited assurance – allow compatibility with the European Union (EU) Corporate Sustainability Reporting Directive (CSRD), ISSA 5000 does not incorporate requirements unique to Europe, such as the green and digital taxonomies. “We anticipate that jurisdictions will add on requirements to meet their regulatory mandates.”
The IAASB is releasing a package of guidance, support videos and outreach activities relating to ISSA 5000 from January 2025.
ICAEW will be hosting an event on Monday 3 March 2025 at Chartered Accountants’ Hall focusing on ISSA 5000 and new International Ethics Standards for Sustainability Assurance (IESSA) from the International Ethics Standards Board for Accountants (IESBA). The event will be free to members. Learn more and book your place.
Guidance from the IAASB
ISSA 5000 (including conforming and consequential amendments to other IAASB standards) and the Basis for conclusions
ISSA 5000: the application of materiality by the entity and the assurance practitioner. A comprehensive set of FAQs
ICAEW resources
Sustainability assurance – the Audit and Assurance Faculty hub of news and insights, standard-setting, helpsheets, guidance and other resources
The sustainability and assurance reporting landscape – Audit & Beyond primer on new and emerging regulations, standards and support resources
European sustainability reporting and assurance – a CSRD overview
Free CPD: sustainability reporting resources – a guide to ICAEW resources on sustainability reporting requirements
