Australian accounting firms face a rapidly evolving demand for credible sustainability reporting as mandatory climate-related disclosures under AASB S2 enter their second year of phased rollout in 2026. With assurance requirements now applying to governance, strategy risks and Scope 1 and 2 emissions in the initial reporting period, many practices are preparing for the transition from limited assurance to full reasonable assurance by 2030.
This growing need for verification expertise creates both a challenge and an opportunity. Accountants who build internal capabilities or establish effective partnerships can help clients deliver reliable disclosures, reduce greenwashing risks and meet rising stakeholder expectations for transparent, assured sustainability information.
The Phased Assurance Requirements Under AASB S2
The Corporations Act amendments require independent assurance of sustainability reports, with the Australian Auditing and Assurance Standards Board (AUASB) setting a staged pathway through ASSA 5010. In the first year of reporting, limited assurance applies at minimum to governance disclosures, descriptions of climate-related risks and opportunities, and Scope 1 and Scope 2 greenhouse gas emissions.
Subsequent years progressively expand coverage: Year 2 brings limited assurance across all disclosures, while Year 3 introduces reasonable assurance on most elements, reaching full reasonable assurance on the entire sustainability report by Year 4 (financial years commencing on or after 1 July 2030 for the final legislative requirement).
This structured progression mirrors international developments and aims to build confidence in reported data while allowing entities and their assurance providers time to strengthen processes and controls.
Why Credible Assurance Matters and the Risks of Getting It Wrong
Assured disclosures enhance the reliability of climate-related information for investors, lenders and regulators. ASIC’s ongoing surveillance under Regulatory Guide 280, combined with its history of greenwashing interventions, highlights the consequences of unsubstantiated or misleading sustainability claims. Reports show that insufficient evidence for emissions profiles, transition plans or risk assessments can lead to regulatory action and reputational damage.
For accounting practices, the credibility challenge extends beyond compliance. Clients increasingly expect their accountants to support not only preparation but also the verification process, ensuring data integrity matches the rigour applied to financial statements.
Industry bodies such as CA ANZ and CPA Australia note that accountants are uniquely positioned to lead in this space, given their existing expertise in governance, risk management and financial controls.
Building Assurance Capabilities: Practical Pathways for Accountants
Many firms are taking a deliberate approach to develop ESG verification skills while maintaining service quality. Common strategies include:
- Investing in targeted professional development through CA ANZ’s Sustainability Playbook, CPA Australia ESG micro-credentials and AUASB guidance on ASSA 5000 and ASSA 5010.
- Updating internal methodologies to incorporate sustainability-specific controls, such as data validation for emissions calculations and documentation of scenario analysis assumptions.
- Conducting pilot assurance engagements on non-mandatory elements ahead of regulatory deadlines to test processes and identify gaps.
- Establishing clear independence and ethical frameworks that align with both financial audit standards and new sustainability assurance requirements.
These steps help practices strengthen their own assurance offerings while advising clients on readiness, such as implementing robust governance oversight and integrating climate data into existing financial control environments.
Some firms also explore collaborative models, working alongside specialist assurance providers during the transition period to ensure high-quality outcomes without overextending internal resources.
Partnering Effectively to Meet Growing Demand
Where building full in-house expertise takes time, many practices partner with experienced providers to deliver credible verification services. This approach allows accountants to focus on client strategy, data preparation and integration with financial reporting while leveraging external specialists for the technical assurance elements.
Successful partnerships typically involve clear scoping of roles, joint training on AASB S2 requirements and shared use of digital tools for data collection and evidence gathering. The result is efficient delivery of limited or reasonable assurance that meets AUASB standards and builds client confidence.
By combining deep client knowledge with specialised verification skills, accountants can help organisations avoid greenwashing pitfalls and position themselves as trusted advisors in the evolving sustainability landscape.
Sources
AUASB Australian Standard on Sustainability Assurance ASSA 5010 Timeline for Audits and Reviews of Information in Sustainability Reports (January 2025).
EY Mandatory Climate-related Financial Disclosures Update and Summary (July 2025).
CA ANZ Sustainability Assurance resources and Sustainability Playbook (2025).
CPA Australia Sustainability (ESG) professional development and guidance materials (2025).
ASIC Regulatory Guide 280 Sustainability Reporting (March 2025).
Frequently Asked Questions
When does reasonable assurance become mandatory for sustainability reports in Australia?
Full reasonable assurance on the entire sustainability report is required for financial years commencing on or after 1 July 2030 under the Corporations Act, with phased progression to this level from Year 4 of reporting under AUASB ASSA 5010.
What is assured in the first year of AASB S2 reporting?
In Year 1, limited assurance applies at minimum to governance disclosures, descriptions of climate-related risks and opportunities (specific paragraphs of AASB S2), and Scope 1 and Scope 2 GHG emissions.
How can accounting firms prepare for the growing demand for ESG assurance?
Firms build capabilities through professional development such as the CA ANZ Sustainability Playbook and CPA Australia ESG courses, while strengthening internal controls and considering collaborative partnerships with verification specialists.
What are the main risks if assurance is not obtained or is inadequate?
Inadequate assurance increases exposure to greenwashing claims under ASIC surveillance, potential regulatory action, and loss of stakeholder trust in the reliability of climate-related disclosures.
Do all entities follow the same assurance timeline?
The same phased pathway applies to Group 1, 2 and 3 entities, though start dates differ (from 1 January 2025 for Group 1). Group 1 entities with January–June year-ends may apply Year 1 requirements for their first two reports.
