The Big 4 accounting firms (KPMG, EY, Deloitte, PwC) are already deeply engaged in helping large companies navigate climate disclosure, sustainability assurance, and the transition to mandatory regimes like AASB S2. Their thought leadership and client guidance are early indicators of what the market will expect. Below is a quick comparison of their consensus views, areas of divergence, and some cautions — particularly for smaller or mid-tier firms.
What they broadly agree on
- Mandatory disclosure is coming — readiness is urgent
- All firms emphasise that entities should begin preparation now for mandatory climate disclosures starting from 1 January 2025 (for Group 1 entities). (EY)
- They highlight that climate risk must be integrated into financial reporting, not treated separately. Deloitte states that management and boards need to connect sustainability risks with financial impact. (Deloitte)
- Practical tools, checklists, illustrative examples
- Governance, board oversight, and senior accountability
- Assurance / audit as part of the regime
- They anticipate that climate disclosures will attract assurance requirements, phased in over time. AUSB’s new sustainability assurance standard (ASSA 5010 / ASSA 5000) has been referenced. (KPMG)
- The Big 4 often position themselves as early movers capable of assurance on climate metrics.
Where their advice or emphasis differs
| Firm | Unique emphasis or angle | Potential contrast or risk |
|---|---|---|
| EY | Deep on illustrative examples, detailed checklists, bridging global & local (IFRS/ISSB + AASB) (EY) | Their examples may assume large, resource-rich companies — smaller firms may find them harder to apply fully. |
| KPMG | Emphasis on trends, external environment, benchmarking (KPMG “Sustainability Reporting Trends”) (KPMG Assets) | Their trend reports may skew toward big clients, making small firm relevance less obvious. |
| Deloitte | Focus on readiness and linking climate risk to financial impact; workforce / capability dimensions (Deloitte) | Their client readiness prescription may require expensive investments in data, systems — beyond what small firms can immediately afford. |
| PwC (where visible) | Less visible in what I found (fewer published checklists), but likely similar to others in pushing alignment with global IFRS/ISSB framework. | Their services often bundle consulting + assurance — may be expensive for smaller clients. |
What small-to-medium firms should heed (and worry about)
- Cost barrier / affordability risk
The Big 4 bring premium experience and resources (global networks, data tools, assurance capacity). For many small or medium enterprises, their fees may be prohibitive. - Capability gap
Big firms already have teams with climate, carbon, sustainability, and assurance expertise. Many smaller audit firms or accounting practices may not yet have trained staff or tools. - One-size-fits-all models
Big 4 guidance often reflects large clients with robust data infrastructure; smaller firms will struggle to scale that model directly without adjustment. - Quality & variation
While all four are experienced, there’s still uncertainty over consistency in climate assurance practices. When my research is published, I expect to comment (high-level) on variation in quality, methods, and what “sufficient assurance” actually means in practice.
Closing thoughts
In short: the Big 4 are doing crucial work, setting foundations, and pushing the market forward on climate reporting and assurance. For large companies, their offering is very likely the “go-to” option. But for many small to medium businesses, the cost and complexity may make them prohibitive. And as the regime scales, there is room — and need — for mid-tier firms, specialist assurance providers, and new entrants to close the gap.
My research (once published) will also cast light on differences in quality, technique, and robustness across providers — especially beyond the Big 4.
