Mandatory Climate Reporting: How Australia's AASB S2 Compares to UK SDR, EU CSRD, and US SEC

If you're a CFO or sustainability lead at an Australian group with operations in the UK, Europe, or the US, you now have to think about four distinct mandatory climate reporting regimes. They all descend from TCFD. They all touch ISSB. They are not the same standard.

The differences sit in four places: who has to report, when, what they have to disclose, and what level of assurance is required. Get the comparison wrong and you either over-collect data (paying for compliance you don't owe) or under-collect data (missing requirements that flow back through subsidiary boards). Most cross-border groups end up somewhere between the two without fully realising it.

Here's the comparison in 2026, with the important caveat that the US position has changed materially in the past 12 months.

Australia: AASB S2 phased by entity size

The Australian Sustainability Reporting Standards consist of AASB S1 (general sustainability) and AASB S2 (climate). For mandatory reporting, only AASB S2 is in force. AASB S1 is voluntary.

Application thresholds are set out in section 296A of the Corporations Act 2001:

Group	Annual revenue threshold	First reporting period
Group 1	$500m+ revenue OR $1bn+ assets OR 500+ employees	FY beginning 1 Jan 2025
Group 2	$200m+ revenue OR $500m+ assets OR 250+ employees	FY beginning 1 Jul 2026
Group 3	$50m+ revenue OR $25m+ assets OR 100+ employees	FY beginning 1 Jul 2027

NGER reporters are automatically pulled into Group 2 regardless of size thresholds.

Assurance follows ASSA 5010 with a phased uplift from limited to reasonable assurance over four years. Modified liability provisions provide some protection for forward-looking disclosures in early years.

Director liability sits in the standard Corporations Act framework, with the modified liability shield specifically for AASB S2 forward-looking statements.

United Kingdom: SDR and the existing TCFD requirements

The UK regime is more fragmented than AASB S2. There are essentially three layers:

Premium-listed companies and AIM. The Listing Rules have required TCFD-aligned disclosure since 2021 on a comply-or-explain basis. From 2022 this became mandatory.

Large companies and LLPs. The Companies (Strategic Report) (Climate-related Financial Disclosure) Regulations 2022 require TCFD-aligned climate disclosure for companies with 500+ employees and £500m+ turnover.

Sustainability Disclosure Requirements (SDR). The Financial Conduct Authority's SDR rules apply primarily to FCA-regulated firms (asset managers, investment products) and require sustainability labels and product-level disclosure. The SDR is not a corporate climate reporting standard in the same shape as AASB S2. The UK has signalled intent to adopt UK Sustainability Reporting Standards based on ISSB, but the standards are not yet finalised as of early 2026.

For an Australian parent with a UK subsidiary, the practical implication: if the UK subsidiary is a large company by the £500m turnover test, it has to make standalone TCFD-aligned disclosure in its UK annual report, even though the Australian parent is also disclosing under AASB S2. The UK disclosure follows TCFD's structure (governance, strategy, risk management, metrics and targets) but does not require the same level of granularity on Scope 3 or scenario analysis as AASB S2.

European Union: CSRD and the ESRS

The Corporate Sustainability Reporting Directive (CSRD) is the most demanding of the four regimes by a wide margin. It requires reporting against the European Sustainability Reporting Standards (ESRS), which cover environment, social, and governance topics with double materiality.

CSRD application:

• Wave 1 (FY 2024): Large EU companies already subject to NFRD (~11,700 companies)
• Wave 2 (FY 2025): Other large EU companies meeting two of three criteria (€50m+ turnover, €25m+ assets, 250+ employees)
• Wave 3 (FY 2026): Listed SMEs with simplified standards
• Wave 4 (FY 2028): Non-EU parents with significant EU activity

The omnibus simplification proposals released in late 2024 and finalised through 2025 have softened wave 2 and wave 3 timing for many companies, but the underlying scope remains broader than AASB S2.

ESRS requires double materiality assessment: financial materiality (ISSB-style) plus impact materiality (the company's effect on the environment and society). AASB S2 is single materiality (financial only). For an Australian parent with a CSRD-reporting EU subsidiary, this means the subsidiary's disclosure includes content that the Australian parent's AASB S2 disclosure does not, particularly around impact materiality on biodiversity, pollution, and social topics.

Assurance is mandatory limited assurance from year one of CSRD application, transitioning to reasonable assurance later.

United States: the SEC climate rule, on hold

The US position has changed dramatically in 2025. The SEC's climate-related disclosure rule, adopted in March 2024, was paused during litigation in 2024. In early 2025 the SEC voted to end its defence of the rule. As of early 2026 the rule is effectively not in force, although it has not been formally rescinded.

What this means in practice: US-listed companies and US subsidiaries of foreign-listed companies do not currently have a federal mandatory climate disclosure obligation through the SEC. They may still be subject to state-level requirements (most notably California's SB 253 and SB 261, which require climate disclosure for large companies operating in California). They may also be subject to investor expectations and continued voluntary TCFD or ISSB-aligned disclosure.

For an Australian parent with a US subsidiary, this means the federal SEC rule is not currently a compliance burden. But California's SB 253 (Scope 1, 2, and 3 disclosure) and SB 261 (climate-related financial risk disclosure) apply to companies doing business in California with revenue over USD 1bn (SB 253) or USD 500m (SB 261). Many Australian groups have US subsidiaries that meet these thresholds.

The California rules' methodology is closely aligned with TCFD and ISSB, so the data prepared for AASB S2 largely fits California's requirements with limited rework.

Where the four regimes actually diverge

Dimension	AASB S2	UK CFD/SDR	EU CSRD	US SEC / California
Materiality	Financial	Financial	Double (financial + impact)	Financial
Scope 3	Required (phased)	Limited	Required	SB 253 yes, SEC rule paused
Scenario analysis	Required, multiple scenarios	Required	Required, more prescriptive	SB 261 limited; SEC paused
Assurance	Phased limited→reasonable	None federal	Limited from year 1	SB 253 limited from 2026
Director liability	Modified for AASB S2 forward-looking	Strategic report standard	National variations	Federal litigation risk paused

The pattern: financial materiality is converging globally, but EU CSRD goes further with impact materiality. AASB S2 sits in the middle of the strictness spectrum.

What this means for an Australian-headquartered global group

The practical consequence for a global group reporting from Australia:

One consolidated emissions data set. Whatever the differences in the standards, the emissions numbers themselves should be the same across all disclosures. Scope 1, 2, and 3 figures by entity and consolidated.

Separate disclosure documents per regime. The same numbers, presented in different formats, with regime-specific narrative content.

Different assurance engagements. CSRD requires limited assurance from year one. AASB S2 has its own phased assurance regime. UK has none federally. The same Big 4 firm typically handles all assurance engagements but the engagement letters and procedures differ.

Different materiality conclusions. A topic that's financially material under AASB S2 might also be impact-material under CSRD, requiring additional disclosure in the EU document.

The data system that supports this is one continuous emissions ledger feeding multiple disclosure outputs. We've covered this pattern for trans-Tasman groups and the same logic applies to global groups with broader footprints.

The CBAM overlay for exporting groups

Australian groups exporting steel, aluminium, cement, fertiliser, hydrogen or electricity to the EU have a fifth regime to navigate: CBAM. CBAM is not a corporate climate disclosure standard. It's a product-level carbon border tax. But the same underlying emissions data feeds CBAM declarations, AASB S2 disclosure, and EU CSRD disclosure if the entity has an EU subsidiary.

The data discipline that handles all of these from one source is the same. The reporting outputs are different.

Practical sequence for a global group

If your group is reporting under multiple regimes:

1. Map your subsidiaries to regimes. Which entities have to file which disclosures, when, and to whom?
2. Define the consolidation rule for each regime. AASB S2 lets the parent choose. CSRD has its own scope rules. The two might give different consolidated entities.
3. Run one continuous emissions ledger. Tagged by entity, jurisdiction, scope, and consolidation method. Feeds all disclosures.
4. Document the methodology consistently. Where regimes diverge, document the divergence and the basis for it.
5. Coordinate assurance. Same firm where possible, with engagement letters that anticipate the cross-regime nature of the work.
6. Watch the change calendar. The four regimes are still moving. ISSB adoption progress in the UK, omnibus updates in the EU, and California implementation rules will all change the picture across 2026 and 2027.

The bottom line

Australia's AASB S2 is the central piece for an Australian parent. It anchors the group's climate disclosure architecture. The UK, EU, and US (where applicable) requirements layer on top, and the differences are real but manageable if the underlying data is right.

The trap is treating each regime as a separate project run by a different team. The fix is treating them as different views of one consolidated emissions data set, with regime-specific narrative content layered over the top.

If you're an Australian-headquartered group running parallel sustainability reporting processes for AASB S2, CSRD, and California disclosures, email hello@carbonly.ai or join the waitlist. Happy to walk through the multi-jurisdiction data architecture that lets one source of truth support every disclosure.