Sustainability Assurance

Issued: September 2025

Overview

This page provides:

1. Background information on sustainability reporting and assurance requirements; and
2. Links to the AUASB’s implementation, guidance and education materials on sustainability assurance.

Background Information

• Mandatory climate reporting

Mandatory climate reporting under the Corporations Act 2001 (the Act) commences at different times for each of three groups of entities.

Reporting commences with the largest entities for financial years beginning on or after 1 January 2025.  The table below shows the criteria for each group and the commencement dates for reporting.

 

• Reporting Requirements

The Act requires annual reports to include a sustainability report that contains the elements shown in the diagram below.

 

AASB S2 Climate-related Disclosures is mandatory for sustainability reporting under the Act.  AASB S1 General Requirements for Disclosure of Sustainability-related Financial Information is voluntary. AASB S2 includes those parts of AASB S1 relevant to climate disclosures.

AASB S1 and AASB S2 standards are based on ISSB standards.  Links to AASB and ISSB materials that may assist in applying AASB S1 and S2 can be found at AASB and ISSB Guidance and Education Materials.

• ASSA 5000

The AUASB’s ASSA 5000 General Requirements for Sustainability Assurance Engagements (issued 28 January 2025 and amended to July 2025) (ASSA 5000) is based on the IAASB’s ISSA 5000 General Requirements for Sustainability Assurance Engagements. 

ASSA 5000 applies to assurance engagements of sustainability information as follows:

1. Information presented in a sustainability report under Chapter 2M of the Act - For periods beginning from 1 January 2025 and as at the end of that period;
2. All other engagements – As at a specified date on or after 31 December 2025 and for periods ending on that date, except where the period commenced before 1 January 2025.

ASSA 5000 applies to both mandatory and voluntary assurance.

However, ASSA 5000 does not apply for assurance over information reported to the Clean Energy Regulator. Instead, a version of ASAE 3000 Assurance Engagements Other than Audits or Reviews of Historical Financial Information applies.

 

• Phasing of assurance for mandatory reporting

For mandatory climate reporting under the Act, ASSA 5000 is subject to the phasing in of limited and reasonable assurance under the AUASB’s ASSA 5010 Timeline for Audits and Reviews of Information in Sustainability Reports under the Corporations Act 2001.

ASSA 5010 specifies the phasing in of assurance for each of the three groups of reporting entities (earlier assurance permitted).  The following table summarises the phasing in of assurance.

ASSA 5010 does not require the directors’ declaration on the sustainability report to be covered by assurance reports for Year 1.

The AUASB is considering:

1. Whether assurance reports should cover the directors’ declaration for years commencing 1 July 2026 to 31 December 2027 when the directors only need to opine on whether the entity has taken ‘reasonable steps’ to ensure compliance with the sustainability reporting requirements of the Act (including AASB S2); and
2. How the phasing in of assurance would apply if the proposals in the Treasury Laws Amendment (Strengthening Financial Systems and Other Measures) Bill 2025 introduced into Parliament on 4 September 2025 are enacted and an entity elects to report early under the Act.

Implementation, guidance and education materials

The AUASB provides the following materials to assist with preparing for assurance over information in sustainability reports under the Act.

• Key messages

Th AUASB's Key Messages for auditors and preparers of sustainability reports.

• Frequently asked questions (FAQs)

The FAQs supplement ASSA 5000 by dealing with complex questions for assurance on information reported under the Act (including AASB S2).

• Illustrative assurance reports

The Illustrative Sustainability Assurance Reports available or under development include illustrative Corporations Act reports for each of the years covered by the phasing in of assurance under ASSA 5010.

• Education materials

The Sustainability Assurance Education Materials are designed to assist auditors in building capability on assurance over information in sustainability reports.