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 finalised rules requiring listed companies to report against them on a comply-or-explain basis 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 October 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. This regime covers accounting periods beginning before 1 January 2027, so a December year-end company makes its last TCFD statement in its 2026 annual report before UK SRS takes over. Our TCFD reporting guide covers the current rule.
- Large companies and LLPs with more than 500 employees: climate-related financial disclosures in the strategic report under the Companies Act. Traded, banking, insurance and AIM companies are caught at that headcount whatever their turnover; other companies and LLPs are caught only if turnover is also above £500 million.
- SECR: quoted companies, and large unquoted companies and LLPs, must report UK energy use and emissions. For financial years beginning on or after 6 April 2025, "large" means exceeding two of three thresholds: £54m turnover, £27m balance sheet, 250 employees (up from £36m and £18m). It is still the broadest net, and the one that quietly catches ordinary mid-size businesses. A 40MWh de minimis spares the smallest energy 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. On their own they are voluntary. What makes them bite is the FCA: its final rules in PS26/19, published on 30 September 2026, replace the TCFD listing rule with a requirement to report against UK SRS S2 and S1 or explain why not, for accounting periods beginning on or after 1 January 2027, with first reports in 2028. That is softer than the January 2026 consultation, which proposed making most of S2 mandatory: the final rules apply comply-or-explain across both standards. Optional transitional reliefs mean issuers need neither comply nor explain on Scope 3 emissions for the first year or on the wider S1 disclosures for the first two years, but they must disclose which reliefs they are using. Our guide to the UK Sustainability Reporting Standards works through the detail and a worked timeline.
For private companies there is still no date. A Companies Act regime extending UK SRS beyond listed companies remains under consideration: the government's Modernising Corporate Reporting consultation, open until 30 November 2026, takes the question forward and floats a new "very large" company category for narrative reporting. Until something is decided, large private companies stay under the existing climate disclosure rules above.
Two satellites are worth tracking. On assurance, the government said in that September 2026 consultation that it has no plans at this stage to require assurance over UK SRS reporting, and it has announced a voluntary oversight regime for sustainability assurance practitioners. The FCA instead makes listed companies say whether they have obtained third-party assurance and, if they have, who provided it, what was assured, to what level and under which standards. Assured data is still the direction of travel; it is just being driven by transparency rather than compulsion. On transition plans, the government is still considering responses to its 2025 consultation on mandating them. 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 December year-end company's first UK SRS period is calendar 2027, and UK SRS has no late-reporting relief, so the disclosures must be published alongside the 2027 financial statements. Emissions data and risk processes for 2027 need to be captured during 2027, not reconstructed in 2028, which makes the rest of 2026 the dry run.
CSRD: smaller than advertised, still real for some
The EU regime that dominated 2024 planning conversations has shrunk. The Omnibus I Directive, Directive (EU) 2026/470, in force since 18 March 2026, cuts CSRD's scope to companies with over 1,000 employees and €450 million net turnover. Second-wave companies that remain in scope report for financial years starting on or after 1 January 2027, and member states have until 19 March 2027 to transpose the changes. UK groups are caught through large EU subsidiaries, or as third-country parents with EU turnover above €450 million and an EU subsidiary or branch with turnover above €200 million. 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 rules give it a one-year relief: use it to build, not to wait;
- Put sustainability data under financial-reporting-grade controls. Listed companies must now disclose any assurance they obtain, Provision 29 declarations already reach this data, and restating your emissions is a worse look each year;
- Version your claims. Anti-greenwashing enforcement targets the gap between marketing and evidence, so 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 investors start asking who checked them. 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. For boards squaring this with Provision 29, the corporate governance side joins the same conversation.