The International Auditing and Assurance Standards Board (IAASB) has taken a significant step forward in sustainability reporting with the approval and issuance of the International Standard on Sustainability Assurance (ISSA) 5000, General Requirements for Sustainability Assurance Engagements. Effective for periods beginning on or after December 15, 2026, ISSA 5000 establishes a comprehensive framework for assurance engagements on sustainability information, marking a pivotal moment in the evolution of global sustainability reporting.

ISSA 5000 serves as an overarching standard, providing baseline requirements for sustainability assurance engagements from start to finish—ranging from acceptance and continuance to reporting. It is designed to be framework-neutral, meaning it can be applied to sustainability information prepared under any suitable reporting framework, including the International Financial Reporting Standards (IFRS) Sustainability Standards, the European Union Corporate Sustainability Reporting Directive (CSRD), and the Global Reporting Initiative (GRI), among others. This flexibility ensures its applicability across diverse jurisdictions and reporting contexts.

The standard addresses a wide array of sustainability topics, including environmental, social, economic, and governance matters, as well as specific aspects such as risks, opportunities, and key performance indicators (KPIs). It also accommodates both limited and reasonable assurance engagements, reflecting the varying levels of assurance demanded by different stakeholders.

Key features of ISSA 5000

1. Framework neutrality

ISSA 5000 is not tied to any single reporting framework, making it adaptable to various global and entity-specific criteria. This ensures its relevance across different regulatory environments and industry practices.

2. Comprehensive scope

The standard applies to all sustainability matters and aspects, including group sustainability engagements. It recognises the importance of value chain considerations, requiring practitioners to assess information from entities both within and outside the reporting entity’s control.

3. Dual assurance levels

ISSA 5000 accommodates both limited and reasonable assurance engagements. It clearly differentiates the requirements and application material for each level, ensuring clarity and consistency in practice.

4. Quality and ethical compliance

Practitioners must comply with quality management standards, such as ISQM 1, and ethical requirements, including the IESBA Code. This ensures the integrity and reliability of sustainability assurance engagements.

5. Materiality considerations

The standard introduces a bifurcated approach to materiality, requiring practitioners to determine materiality for quantitative disclosures and consider it for qualitative disclosures. This approach acknowledges the unique nature of sustainability information, which often includes both numerical data and narrative explanations.

6. Risk assessment and evidence gathering

ISSA 5000 mandates rigorous risk assessment procedures tailored to the level of assurance being provided. It also provides guidance on obtaining sufficient and appropriate evidence, particularly for qualitative and forward-looking information, which is inherently more subjective.

Substantial changes from the exposure draft

The final version of ISSA 5000 incorporates feedback from stakeholders, resulting in several key modifications:

• Withdrawal of ISAE 3410: ISSA 5000 will replace ISAE 3410, which currently governs assurance engagements on greenhouse gas (GHG) statements. The IAASB concluded that ISSA 5000 is sufficiently comprehensive to address GHG-related engagements.
• Group Engagements: The standard introduces specific requirements for group sustainability assurance engagements, recognising the complexities of reporting across multiple entities and value chains.
• Ethical and Quality Management: The final standard emphasises the importance of compliance with ethical and quality management requirements, particularly for non-professional accountant assurance practitioners.

Implications for practitioners and entities

ISSA 5000 represents a significant shift in the sustainability assurance landscape. For practitioners, it provides a clear and consistent framework for conducting assurance engagements, reducing ambiguity and enhancing the credibility of sustainability reports. For entities, the standard underscores the importance of robust internal controls and processes for identifying, measuring, and reporting sustainability information.

The standard also addresses the growing demand for transparency and accountability in sustainability reporting. By requiring practitioners to consider both financial and impact materiality, ISSA 5000 aligns with the concept of “double materiality”, which is increasingly recognised as a cornerstone of high-quality sustainability reporting.

As sustainability reporting continues to evolve, ISSA 5000 is expected to play a critical role in shaping best practices and driving consistency across jurisdictions. Its introduction marks a significant milestone in the IAASB’s efforts to enhance the reliability and comparability of sustainability information, ultimately supporting informed decision-making by stakeholders.

With its effective date set for December 2026, entities and practitioners have time to prepare for the transition. However, given the complexity of sustainability reporting and the need for robust systems and processes, early adoption and proactive planning will be essential to ensure compliance and maintain stakeholder confidence.