In December 2026, a new ethics framework for sustainability assurance takes effect globally. If your organisation is commissioning sustainability assurance, or if your firm provides it, IESSA Part 5 will reshape how independence is managed and disclosed.
What’s Changing
IESSA Part 5 introduces dedicated independence requirements for all sustainability assurance practitioners—not just accountants. This matters because the boundaries between advising on sustainability strategy and assuring sustainability claims are becoming formally defined.
For many organisations, this is straightforward: if you have worked with a firm on designing your sustainability targets or measurement systems, you will want to know whether the same firm can still independently assure your reported performance. In many cases under IESSA Part 5, the answer is no — not because of a documentation gap, but because the standard treats this specific conflict as one that cannot be fixed with safeguards. This is a materially different position from most other independence conflicts, which can typically be managed through disclosure and team separation.
Why Independence Matters in Sustainability
Unlike financial audit, which has a long-established independence tradition, sustainability assurance is defining its professional standards now. Stakeholders—investors, regulators and civil society—increasingly expect assurance over ESG claims to be genuinely independent.
When a practitioner designs your GHG measurement methodology and later assures your emissions data, that is not third-party verification. It is quality control with a professional stamp. IESSA Part 5 treats this specific scenario strictly: for listed and other public interest entities, the standard generally prohibits the same firm from doing both. For other entities, the same outcome often applies in practice, unless the original advisory work was purely routine or mechanical.
For Audit Committees and Governance Teams
If you are overseeing sustainability assurance engagements, do not assume that a disclosed conflict is an acceptable one. Some prior advisory relationships between your firm and its assurance provider cannot be resolved through safeguards at all — the firm may need to step back from the assurance role, or a different firm may need to be engaged.
Your role is to:
- Establish early whether any prior advisory work could create a self-review threat that cannot be safeguarded
- Understand the nature of prior advisory work and whether it involved genuine judgment or was purely mechanical
- Require your assurance provider to demonstrate, not just assert, that independence has been maintained
South African firms regulated by IRBA will face scrutiny on these disclosures during quality reviews.
For Audit and Assurance Firms
IESSA Part 5 requires action now:
- Map your advisory relationships. Which sustainability assurance clients have also received advisory services that could affect the information you’d be assuring? Flag these for immediate review — some may need to be unwound or reassigned to a different firm entirely.
- Understand where safeguards will nott help. Not every conflict can be documented and safeguarded away. Know which scenarios in your client base fall into the “cannot be managed” category before you are mid-engagement.
- Update policies. Do your independence policies explicitly address sustainability assurance threats, not just financial audit?
- Train your teams. Staff conducting sustainability assurance need to understand IESSA Part 5, especially where the rules are stricter than they may expect from financial audit experience.
Implementation should already be underway—December 2026 is approximately three months away, and IRBA inspections will include this framework.
For Specialist Practitioners
If you are an environmental consultant, engineer, or specialist assuring sustainability metrics, IESSA Part 5 now applies to you. Whether or not IRBA regulates you, clients and stakeholders will increasingly expect compliance with this standard. Professional credibility depends on it.
What’s Next
The standard is coming. With December 2026 approaching, firms and organisations should:
- Now: Identify advisory engagements and assess independence implications; update policies and train staff
- Before 15 December 2026: Communicate with clients about independence policies, and resolve any arrangements that cannot be safeguarded
- From 15 December 2026: Apply IESSA Part 5 to all sustainability assurance engagements
This article reflects the regulatory position as of September 2026. Practitioners should consult primary sources (the IRBA Code of Professional Conduct, Part 5; ISSA 5000; IRBA.co.za) for authoritative guidance.
