ISSA 5000 and sustainability assurance
What ISSA 5000 is, when the IAASB says it takes effect, and the skills and quality questions a firm should answer before offering sustainability assurance.
By Achekam · · 4 min read · For Accountants & audit firms in South Africa, Nigeria, Kenya
A client's main customer has started asking for an emissions figure in its supplier questionnaire. Another client's lender wants a short report on water use and staff safety alongside the annual financial statements. Neither asks for assurance yet. But both are the kind of request that tends to grow into "and can someone independent check this?", and the client will ask its auditor first.
The IAASB now has a standard written for exactly that work. This article explains where ISSA 5000 sits, when it takes effect, and the questions a firm should answer honestly before it offers sustainability assurance.
ISSA 5000 in Volume 3 of the 2026 Handbook
The IAASB's 2026 Handbook of its pronouncements comprises five volumes, and Volume 3 contains International Standard on Sustainability Assurance (ISSA) 5000, General Requirements for Sustainability Assurance Engagements. The IAASB's page for the 2026 Handbook lists the volumes and gives access to them.
The placement says something. ISSA 5000 sits in Volume 3, apart from the auditing standards in Volume 1. It is a standard for a different kind of engagement, one whose subject is sustainability information rather than the financial statements, and firms should approach it as a new service with its own requirements rather than an extension of the audit.
Effective in December 2026
The IAASB states that ISSA 5000 becomes effective in December 2026 and is included in the 2026 Handbook, alongside ISA 240 (Revised) and ISA 570 (Revised 2024), which take effect at the same time.
Two practical points follow. First, read the standard's own effective-date wording before agreeing terms for any engagement near that date. Second, as with every IAASB pronouncement, whether and how ISSA 5000 applies in a given country depends on local adoption. Check the position with IRBA in South Africa, the FRC and ICAN in Nigeria, or ICPAK in Kenya before describing any engagement as performed under it.
COSO guidance on internal control over sustainability reporting
An assurance engagement depends on what the client can support. COSO states that in 2023 it issued supplemental guidance for organisations to achieve effective internal control over sustainability reporting, using its Internal Control — Integrated Framework.
That guidance is useful to a firm in two ways. It gives the firm a vocabulary for understanding how a client gathers, checks and reports sustainability data, much as the framework already does for financial reporting. And it gives clients something concrete to work towards before they ask for assurance. A client whose emissions figure comes from one spreadsheet maintained by one person, with no review, is not ready for assurance, whatever standard the firm intends to use.
Skills and quality management questions for the firm
Before offering sustainability assurance, a partner group should be able to answer these questions plainly:
- Competence. Who in the firm understands the subject matter, whether energy, emissions, water or labour practices, well enough to judge whether the information is reasonable? Where will the firm get expertise it lacks?
- Methodology. Does the firm have, or can it build, working papers and procedures written against ISSA 5000 itself?
- Quality management. Has the firm considered sustainability engagements in its own system of quality management, including acceptance, supervision and review?
- Independence and ethics. Where the assurance client is also an audit client, or the firm helped prepare the information, what threats arise and how will they be dealt with?
- Acceptance. For each client, is the information prepared on suitable criteria, and are the records good enough to support an assurance conclusion?
- Commercial reality. Is there enough demand among the firm's clients to justify the investment?
Answering "not yet" to several of these is not failure. It is a plan.
What Achekam's packs cover today: ISAE 3000, not ISSA 5000
Be clear about the tools. Achekam ships working-paper template packs written in its own words, for a firm to adopt and approve, covering among other things ISAE 3000. Its packs list ISAE 3000, not ISSA 5000; there is no ISSA 5000 pack. Any firm planning sustainability assurance under ISSA 5000 would need to build its own working papers from the standard. The catalogue that does exist is marked as unapproved platform content until the firm adopts it.
On the engagement side, staff choose an engagement's type when creating it, such as an annual financial statements compilation, an independent review or a statutory audit, and a firm can add its own named types. A firm that takes on sustainability work can therefore record it as its own type of engagement rather than forcing it under an audit heading. For the general assurance standard many firms already use, see assurance engagements under ISAE 3000.
First steps for an interested firm
- Read ISSA 5000 in Volume 3 of the 2026 Handbook, starting with its scope and requirements, and note what is new to the firm.
- Ask a few existing clients what sustainability information they already produce, and for whom.
- Read COSO's supplemental guidance on internal control over sustainability reporting, and use it to judge how ready those clients are.
- Decide, with the partners, whether to build the service, partner with a specialist or stay out for now.
- If building, draft the methodology from the standard, route it through the firm's own template approvals, and run a pilot on a willing client with modest information.
- Track local adoption, and do not describe work as performed under ISSA 5000 until that position is clear.
For the wider context of this year's IAASB changes, see the IAASB 2026 Handbook. Sustainability assurance may not be a large part of a small practice's work this year. The firms that read the standard now will be the ones ready when a client's lender stops asking politely.
General guidance only, not advice on your own circumstances. Tax and payroll rules change: check the current position with the authority or your adviser.
