How to get started with ESG assurance in Australia: A step-by-step guide

As Australia moves toward mandatory climate-related disclosures, ESG assurance is shifting from a future consideration to a near-term priority for audit firms. The question is no longer whether firms will need to engage with it, but how quickly they can do so with confidence.

For many, the difficulty is not understanding the importance of ESG assurance. It is knowing where to begin. Unlike financial audits, there is no deeply embedded, ESG-specific playbook. What exists instead is a mix of emerging standards, evolving expectations and, in many cases, data that has not been prepared with assurance in mind.

The result is that firms are often approaching early engagements without a clear, repeatable structure. That has implications not just for efficiency, but for consistency and risk.

What is ESG assurance?

ESG assurance is the process of assessing whether a company’s sustainability disclosures, particularly climate-related information, are complete, accurate and supported by evidence. It involves evaluating data sources, controls and assumptions to determine whether disclosures can be relied on by stakeholders.

Why ESG assurance is becoming a near-term requirement

Regulatory momentum in Australia is building. Proposed climate-related financial disclosures, aligned to ISSB standards, will bring large entities into scope first, with assurance expectations expected to develop alongside these disclosures.

For audit firms, this creates a practical challenge. Clients are preparing for disclosure, and reporting timelines are not shifting. Many teams are being asked to support ESG-related assurance ahead of the 30 June cycle, often before internal approaches have fully formed.

This is not a distant transition. It is already underway.

ESG assurance: key steps for audit teams

1. Define scope and applicable standards (e.g. ISSB, climate-related disclosures
2. Identify required disclosures, including risks, metrics and governance
3. Gather and assess supporting evidence from underlying data sources
4. Document procedures, judgements and conclusions

What ESG assurance involves in practice

At a high level, ESG assurance is about determining whether disclosures are complete, accurate and supported by evidence. In practice, applying that consistently requires more interpretation than many firms expect.

While existing standards such as ASAE 3000 provide a foundation, their application to ESG disclosures is still emerging. ESG data often sits outside traditional financial systems, is compiled from operational sources, and may not yet be supported by mature controls.

In many first-year engagements, the issue is not the absence of data. It is that the data cannot be traced back to a controlled or auditable source.

This shifts the nature of the work. ESG assurance becomes less about applying a fixed methodology and more about establishing a defensible approach that can be applied consistently.

Preparing for your first ESG assurance engagement

A practical way to approach ESG assurance is to break the engagement into a small number of core stages. Not as a rigid methodology, but as a way to introduce structure early.

Define scope and applicable standards

Start by clarifying what is in scope and which frameworks apply. This typically includes climate-related disclosures, governance and selected metrics, aligned to ISSB or local regulatory guidance. Ambiguity at this stage tends to compound later in the engagement.

Identify required disclosures

Map what the client is expected to report, including climate risks, emissions metrics and governance structures. This requires understanding how disclosures link to underlying business activities and where gaps may emerge.

Gather and assess evidence

Evidence is often fragmented across systems and teams, and not always prepared with assurance in mind. The task is not only to collect information, but to assess whether it is sufficiently robust and traceable to support assurance conclusions.

Document procedures and conclusions

Documentation carries particular importance in ESG assurance. Standards are still developing, and much of the work involves judgement. A clear audit trail should show what was reviewed, how conclusions were reached, and where interpretation was applied.

Common challenges teams encounter early

As firms begin working through ESG assurance engagements, a consistent set of challenges tends to emerge. These are explored in more detail in the most common ESG assurance challenges audit firms are facing, but typically include:

• Interpreting principles-based standards in the absence of clear precedent
• Developing procedures and workpapers from scratch
• Managing ESG work alongside existing audit timelines

These challenges are not unexpected. They reflect a discipline that is still forming in practice.

Introducing structure early

Firms are taking different approaches to addressing this. Some continue to build their process engagement by engagement. Others are introducing structure earlier to create more consistency.

In practice, this often begins with defining a consistent set of procedures, aligning how disclosures are assessed, and standardising documentation expectations.

One way firms are doing this is through the use of checklists. Not as a substitute for professional judgement, but as a way to establish a baseline and reduce the need to re-interpret requirements for each engagement.

A more detailed view of how this can be applied is captured in a structured ESG assurance checklist for audit teams.

From uncertainty to readiness

ESG assurance practices are still forming at the engagement level, but expectations are already shifting. As climate disclosures become more established, the expectation for assurance alongside them will continue to grow.

Firms that focus on establishing a clear, repeatable starting point are better positioned to build capability over time. Those that delay until practices are fully defined may find themselves responding under greater time pressure.

The shift is not from uncertainty to clarity. It is from uncertainty to readiness.

For a deeper walkthrough, you can also watch the ESG assurance webinar.