One Baseline, Many Rulebooks: Where ISSB Adoption Actually Stands

Twenty eight jurisdictions have adopted the ISSB standards and twelve more are planning to, so the baseline question is settled. The one that is not settled, and that nobody writes about clearly, is what actually happens to a group's reporting calendar when it operates in three of them at once. The answer is not "three times the work". It is stranger than that, and the worked example below shows why the strictest jurisdiction quietly sets the pace for everything else.¹

Last updated 24 August 2026. Adoption counts reflect S and P Global analysis published 7 May 2026, with data as at 22 April 2026. Individual jurisdiction positions are sourced separately below.

Where adoption actually stands

The direction is settled, the pace is not. The S and P Global tracker put 28 jurisdictions in the adopted column as at 22 April 2026, covering both voluntary and mandatory use, with 12 further jurisdictions progressing towards adoption. Recent movement has been concentrated and fast: South Korea issued KSDS 1 and KSDS 2 in February 2026, the United Kingdom published UK SRS S1 and S2 in the same month, and Japan mandated disclosures for listed companies. Bangladesh, Ethiopia and Indonesia advanced consultations or draft roadmaps during the first quarter.¹

The major regimes side by side

Five markets carry most of the practical load for internationally active groups. The table below sets out where each stands. Note the United Kingdom in particular, where the standards exist but the mandate does not yet.

The four differences that actually cost you time

The standards converge, the wrappers do not. Because nearly every jurisdiction begins from IFRS S1 and S2, the disclosure content is broadly consistent. What varies, and what determines how much extra work a second or third jurisdiction creates, comes down to four things.

One: when the report must be published

The ISSB permits sustainability disclosures to be published later than the financial statements in early years. Jurisdictions differ on whether they keep that. Singapore's proposed SFRS S2 removes the relief, expecting climate disclosure at the same time as the financials, which is the single change most likely to strain a mid market close calendar.³

Two: when Scope 3 becomes mandatory

Almost universally deferred, but on different schedules. Singapore requires it of STI constituents from FY2026 and leaves it voluntary for other issuers until further notice, with the proposed standards extending that relief indefinitely for companies outside a mandate. Australia gives a one year relief, so an entity's second reporting year is its first mandatory Scope 3 year.^3,4

Three: when assurance starts, and how hard

This is the widest divergence and the one with the longest lead time. Australia phases assurance under ASSA 5000 on the ASSA 5010 timeline, beginning with limited assurance over Scope 1 and 2 in an entity's first year and reaching reasonable assurance over all mandatory climate disclosures for financial years commencing on or after 1 July 2030. Singapore's listed issuers face external limited assurance on Scope 1 and 2 from FY2029.^4,5

Four: which reliefs the jurisdiction keeps

Transition reliefs, proportionality mechanisms and references to other frameworks all get adjusted locally. Singapore proposes softening the ISSB requirement to refer to SASB material from a requirement to an option. The ISSB's own targeted amendments to IFRS S2, issued in December 2025 and effective for periods beginning on or after 1 January 2027, add further jurisdictional reliefs covering measurement methods and global warming potential values, which each adopting jurisdiction then handles in its own timing.^3,6

Timing, Scope 3 posture, assurance phasing and local reliefs. Map those four per market and the underlying reporting process does not need to change.

What this looks like in practice

Abstract axes are hard to plan against, so here is a concrete group. Take a business with a London listed parent, an Australian subsidiary large enough to fall into Group 2, and a Singapore listed subsidiary that is not an STI constituent but sits above the one billion dollar market capitalisation threshold. Nothing exotic. Map the four variables and this is the calendar that falls out.

Three things fall out of that table that surprise people.

One, the subsidiary reports before the parent. The Singapore entity has been filing mandatory Scope 1 and 2 since FY2025, and the Australian entity begins in mid 2026, while the UK parent's obligation is still a proposal. A group that waits for its home jurisdiction to move has already missed two reporting cycles somewhere else.

Two, Scope 3 arrives for one entity while remaining optional for another. The Australian subsidiary's first mandatory Scope 3 year begins 1 July 2027. On the same date, Scope 3 for the Singapore entity is still voluntary. So the group needs working value chain data collection for part of the business well before any group wide requirement exists, and it makes little sense to build that capability twice.

Three, assurance starts on a fragment of the footprint. The Australian entity faces limited assurance on Scope 1 and 2 from its very first year, in 2027. The Singapore entity is not assured until FY2029. For two years the group is subject to an external opinion on one subsidiary's numbers and not on the others, which means the whole group's method and boundary documentation gets tested through that one entity.

And this is before the timing question. If Singapore's proposal to remove the relief allowing sustainability disclosures to be published after the financial statements is adopted, the Singapore entity's climate report must land with its financials, which pulls the group's data close forward for everyone feeding that entity. One local change to one subsidiary's rulebook resets a group wide process.³

What a multinational should do with this

• Build to the strictest wrapper, not the average one. If one jurisdiction requires simultaneous publication with the financials, that becomes your effective group calendar. Designing to the loosest requirement guarantees rework.
• Track the four axes in a single table, per entity. It is a short document and it prevents the most common failure, which is discovering a local relief does not apply three weeks before filing.
• Treat assurance readiness as the long pole. Reasonable assurance in Australia from financial years commencing 1 July 2030 sounds distant, but assurance is retrospective. Practitioners will test method and boundary consistency against prior years, so the documentation discipline has to start well before the opinion does.⁵
• Do Scope 3 before you are made to. Every jurisdiction defers it, and every jurisdiction eventually requires it. The supplier data work takes longer than one reporting cycle, so the relief period is the time to build rather than the time to wait.
• Watch the consultations, not just the deadlines. Singapore's consultation on SFRS S1 and S2 runs to 25 October 2026, and the FCA's final UK rules are expected in the autumn. Both are moments where a well evidenced submission still changes the outcome.^2,3

Frequently asked questions

How many countries have adopted the ISSB standards?

Analysis by S and P Global counted 28 jurisdictions that had adopted the ISSB standards on a voluntary or mandatory basis as at 22 April 2026, with a further 12 jurisdictions planning adoption.

Is IFRS S1 and S2 reporting mandatory in the United Kingdom?

Not yet. UK SRS S1 and S2 were published on 25 February 2026 by the Department for Business and Trade and are currently available for voluntary use. The FCA has consulted on requiring listed companies to report against UK SRS S2 from 1 January 2027, with final rules expected in autumn 2026. Large private companies are not yet in scope, pending a separate government consultation.

Which countries adopted ISSB standards most recently?

February 2026 was unusually busy. South Korea issued KSDS 1 and KSDS 2, the United Kingdom published UK SRS S1 and S2, and Japan mandated disclosures for listed companies. Bangladesh, Ethiopia and Indonesia advanced consultations or draft roadmaps during the first quarter of 2026.

If the standards are all based on IFRS S1 and S2, why is multi jurisdiction reporting still difficult?

Because the differences are procedural rather than substantive. Jurisdictions vary on when the sustainability report must be published relative to the financial statements, when Scope 3 disclosure becomes mandatory, when assurance begins and at what level, and which transition reliefs and framework references they retain. Those four variables determine the reporting calendar and the evidence requirements, even when the disclosure content is nearly identical.

Do the December 2025 IFRS S2 amendments apply everywhere?

Not automatically. The ISSB issued targeted amendments to IFRS S2 on 11 December 2025, effective for annual reporting periods beginning on or after 1 January 2027 with early application permitted. Each adopting jurisdiction incorporates them on its own timetable, so the effective date in a national standard may differ from the ISSB's.

References

1. S and P Global, Where does the world stand on ISSB adoption? Published 7 May 2026, accessed August 2026.
2. Generation Impact Global, UK ESG law 2026: UK SRS and FCA CP26 slash 5, accessed August 2026.
3. ACRA, Public consultation on Singapore's sustainability disclosure standards, accessed August 2026.
4. AASB, AASB S2 Climate related Disclosures, accessed August 2026.
5. AUASB, Climate and sustainability assurance requirements approved, ASSA 5000 and ASSA 5010, accessed August 2026.
6. IFRS Foundation, ISSB issues targeted amendments to IFRS S2, 11 December 2025, accessed August 2026.

This guide is general information, not legal or accounting advice. Adoption status changes frequently and some measures described are proposals rather than final rules. Check the primary sources above for the current position in your reporting jurisdiction.