ESG reporting in the UK is in the middle of its biggest transition since climate disclosure began: the final UK Sustainability Reporting Standards (UK SRS S1 and S2) were published in February 2026, the FCA has consulted on making them mandatory for listed companies from 2027, and the EU has simultaneously slashed the scope of its own CSRD. For finance teams the practical question is no longer "should we report" but "which of five overlapping frameworks applies to us, from when, and what do we build once instead of five times".
Here is the map as it stands in September 2026 — what is mandatory today, what is coming, and what is still genuinely undecided.
What is mandatory right now
- Listed companies: TCFD-aligned climate disclosure under the FCA's listing rules, on a comply-or-explain basis — the current regime until UK SRS supersedes it.
- Very large companies and LLPs (over 500 employees and £500 million turnover, plus AIM companies over 500 employees): climate-related financial disclosures in the annual report under the Companies Act.
- SECR: quoted companies, and large unquoted companies and LLPs meeting two of three thresholds (£36m turnover, £18m balance sheet, 250 employees), must report UK energy use and emissions — the broadest net, and the one that quietly catches ordinary mid-size businesses. A sub-40MWh de minimis spares the smallest users.
- Regulated firms: the FCA's anti-greenwashing rule has applied since May 2024 — any sustainability claim must be fair, clear and not misleading — with the SDR investment-label regime alongside for asset managers.
- Boards of Code companies: for listed companies reporting against the Corporate Governance Code, Provision 29 asks boards (comply-or-explain) to declare the effectiveness of their material controls from January 2026 reporting periods — and sustainability data increasingly sits inside that declaration's scope.
UK SRS: the new spine
UK SRS S1 (general sustainability disclosures) and S2 (climate) are the ISSB's global standards with modest UK amendments. Today they are voluntary. The direction is not: the FCA consulted in early 2026 on requiring listed companies to report against them for periods starting 1 January 2027 — S2 climate reporting mandatory, the wider S1 disclosures and Scope 3 emissions phased in with comply-or-explain deferrals — with final rules expected this autumn. A Companies Act regime extending UK SRS to large private companies ("economically significant entities") remains an announced intention without scope or date.
Two satellites are worth tracking. On assurance, the government will legislate a registration regime for sustainability assurance providers when parliamentary time allows, with the FRC running a voluntary interim register from mid-2026 — a signal that assured sustainability data is the destination. On transition plans, the 2025 consultation on mandating them has yet to produce next steps; committing to climate targets in print already creates greenwashing exposure, so plans should be written as carefully as accounts.
For listed companies the planning implication is immediate: a 1 January 2027 start means comparative data and processes need building through 2026 — this year is the dry run, whether or not it feels like one.
CSRD: smaller than advertised, still real for some
The EU regime that dominated 2024 planning conversations has shrunk. The Omnibus amendments, in force since March 2026, cut CSRD's scope to companies with over 1,000 employees and €450 million turnover — removing roughly 80% of originally in-scope companies — with the revised requirements applying from FY2027 reporting. UK groups are caught through large EU subsidiaries, or as third-country parents with EU turnover above €450 million and a substantial EU subsidiary or branch. If your CSRD project was scoped in 2024, re-scope it: many UK mid-caps dropped out entirely, while genuinely large EU-exposed groups still face the full double-materiality machine, one jurisdiction's transposition at a time.
Making it manageable: one dataset, many outputs
The businesses handling this well treat the frameworks as different windows onto one underlying dataset — governance, risk processes, metrics and targets — rather than five separate projects:
- Start from the ISSB architecture (governance, strategy, risk management, metrics), because UK SRS is built on it and TCFD folds into it — work done here is portable everywhere;
- Fix the emissions data first. Scope 1 and 2 numbers with an audit trail satisfy SECR today and seed S2 tomorrow; Scope 3 is the long pole, which is exactly why the FCA proposal gives it deferrals — use them to build, not to wait;
- Put sustainability data under financial-reporting-grade controls. Assurance is coming, Provision 29 declarations already reach it, and restating your emissions is a worse look each year;
- Version your claims. Anti-greenwashing enforcement targets the gap between marketing and evidence — the sustainability page and the SECR table should be reconcilable by a stranger.
Where advisers fit
Most mid-size businesses do not need a sustainability department; they need their existing reporting cycle extended to carry this data credibly — scoping which regimes bite, building the emissions baseline, and getting the disclosures assurance-ready before assurance is compulsory. That is reporting work, not campaigning work, and it sits naturally with the people who already run your year-end. Our ESG assurance team covers readiness and verification, with financial reporting handling the annual-report integration — and for boards squaring this with Provision 29, the corporate governance side joins the same conversation.