The short answer
Yes — for many companies, but not through a single law. The UK has no one “sustainability report” that every company must file. Instead, obligations arrive regime by regime, and whether you must report depends on your size, whether you are listed, and how much energy you use.
Three regimes are mandatory now for large and listed organisations: SECR energy and carbon reporting1, TCFD-aligned climate-related financial disclosure3, and ESOS energy audits4.
The newer UK Sustainability Reporting Standards (UK SRS) are voluntary today5 but proposed to become mandatory for listed companies from 20276.
EU CSRD reaches only UK groups with a significant EU footprint7.
Small and medium-sized private companies usually have no mandatory obligation at all — though many report voluntarily to satisfy investors, lenders and customers.
For the full map of every regime in one place, see our reference on ESG reporting requirements in the UK.
What is mandatory now
Three UK regimes already impose mandatory sustainability-related reporting on qualifying organisations.
SECR — energy and carbon reporting
Streamlined Energy and Carbon Reporting has been mandatory since 1 April 2019 under SI 2018/11551.
It applies to three groups: quoted companies of any size, large unquoted companies, and large LLPs1.
In-scope organisations disclose UK energy use, greenhouse-gas emissions and an intensity metric in their annual report2.
Our SECR thresholds guide sets out the two-of-three qualification test, and SECR exemptions covers the low-energy-user relief.
Climate-related financial disclosure
Since accounting periods beginning on or after 6 April 2022, larger companies and LLPs must make TCFD-aligned climate-related financial disclosures under SI 2022/31, which inserted section 414CB into the Companies Act 20063.
This obligation is built on the four-pillar TCFD framework and is the direct predecessor of UK SRS S2.
See UK TCFD requirements for who is in scope.
ESOS — mandatory energy audits
The Energy Savings Opportunity Scheme requires large undertakings to complete energy audits every four years under SI 2014/16434.
ESOS is an audit-and-notify obligation rather than a public report, but it is mandatory, enforced by the Environment Agency, and its Phase 4 deadline is 5 December 2027.
Our is ESOS mandatory guide explains the qualification tests.
What is voluntary — for now
The UK Sustainability Reporting Standards are the newest and most comprehensive framework, but they are not yet mandatory for anyone.
UK SRS S1 and S2 were published by the Department for Business and Trade on 25 February 20265.
On publication they are voluntary — any company may choose to report against them.
The route to mandation runs through two channels: the FCA for listed companies, and Government for other companies.
The FCA’s CP26/5 consultation (closed 20 March 2026) proposes mandatory UK SRS S2 climate reporting for in-scope listed companies from accounting periods beginning on or after 1 January 2027, with Scope 3 on a comply-or-explain basis in the first year6.
The FCA policy statement is expected in autumn 20266. UK SRS S1
is expected to apply on a comply-or-explain basis from 20295.
Our UK SRS timeline tracks each milestone.
Who must report, by company type
The single biggest determinant is size and listing status.
This table summarises the mandatory position for the most common company types.
| Company type | Mandatory now | Becoming mandatory |
|---|---|---|
| Listed company (Main Market) | SECR + climate disclosure (s414CB) [1] [3] | UK SRS S2 proposed from FY2027 [6] |
| Large unquoted company / LLP | SECR (if two-of-three met) + ESOS (if large undertaking) [1] [4] | Government to consult on UK SRS for large companies [5] |
| Large private company using much energy | SECR + ESOS energy audits [1] [4] | Watch UK SRS scope decisions [5] |
| SME (private, below thresholds) | Generally none [1] [3] [4] | Voluntary; supply-chain requests likely |
| UK group with large EU presence | UK regimes as above | CSRD via Article 40a from FY2028 [7] |
If you are unsure which line you sit on, the compliance checker walks through the employee and financial tests, and who must comply with UK SRS covers the listed-company detail.
Are transition plans mandatory in the UK?
Not as a standalone requirement. This is one of the most common points of confusion, so it is worth stating precisely.
The FCA does not propose to mandate the production of a climate transition plan — it regards that as a matter for Government6.
What CP26/5 proposes is narrower: that in-scope listed companies disclose whether they have published a transition plan and, if so, where it can be found6.
In other words, disclosure about a transition plan is proposed, but producing one is not compelled.
In practice, transition-plan content is arriving through UK SRS S2, which carries the strategy and metrics disclosures that a transition plan draws on5.
For the fuller picture, see our guides to transition plans under UK SRS and UK transition plan regulation.
Does EU CSRD make reporting mandatory for UK companies?
Not domestically.
The EU Corporate Sustainability Reporting Directive was never transposed into UK law, so it imposes no direct duty on UK-incorporated companies.
A UK-headquartered group is caught only through the Article 40a third-country route — where its EU net turnover exceeds €450 million in each of the last two consecutive financial years and it has a large EU subsidiary or an EU branch with turnover above €200 million, reporting from financial year 20287.
Our dedicated guide to CSRD for UK companies works through the post-Omnibus tests in full.
How to tell whether you must report
A quick way to place your company:
- Are you a quoted company? If yes, SECR and — for the Main Market — climate-related financial disclosure already apply13.
- Are you a large unquoted company or LLP meeting two of the three SECR criteria (£36m turnover, £18m balance sheet, 250 employees)? If yes, SECR applies1.
- Are you a large undertaking for ESOS (250+ staff, or the turnover and balance-sheet tests)? If yes, mandatory energy audits apply4.
- Are you listed and preparing for 2027? Begin UK SRS S2 readiness now — it is proposed mandatory from that year6.
- Do you have a large EU footprint? Test against the CSRD Article 40a thresholds7.
Frequently asked questions
Are sustainability reports mandatory in the UK?
Partly. There is no single “sustainability report” mandate — obligations come regime by regime. SECR energy and carbon reporting is mandatory now for quoted companies and large unquoted companies and LLPs [1]. TCFD-aligned climate-related financial disclosure has been mandatory since accounting periods beginning on or after 6 April 2022 for premium and standard listed companies and large companies and LLPs [3]. ESOS energy audits are mandatory for large undertakings [4]. The newer UK Sustainability Reporting Standards (UK SRS) are currently voluntary, but the FCA has proposed making UK SRS S2 mandatory for listed companies from accounting periods beginning on or after 1 January 2027 [5] [6].
Is sustainability reporting mandatory for small companies in the UK?
Generally no. SECR, the mandatory climate disclosure rules, and ESOS all target large undertakings and quoted companies [1] [3] [4]. Small and medium-sized private companies usually have no mandatory sustainability reporting obligation, though many report voluntarily because of investor, lender or supply-chain requests. See our guide to SME sustainability reporting for the practical position.
Are sustainability reports required for private companies?
Only if they are large. A large private (unquoted) company or LLP that meets the SECR two-of-three test — turnover of £36m or more, balance sheet total of £18m or more, 250 or more employees — must include SECR energy and carbon information in its report [1], and may also be caught by mandatory climate-related financial disclosure [3] and ESOS [4]. Private companies below those thresholds report voluntarily.
When does UK SRS become mandatory?
UK SRS S1 and S2 were published by the Department for Business and Trade on 25 February 2026 and are voluntary on publication [5]. The FCA’s CP26/5 consultation (closed 20 March 2026) proposes mandatory UK SRS S2 climate reporting for in-scope listed companies from accounting periods beginning on or after 1 January 2027, with Scope 3 on a comply-or-explain basis in the first year; the FCA policy statement is expected in autumn 2026 [6]. UK SRS S1 is expected to apply on a comply-or-explain basis from 2029 [5] [6].
Are transition plans mandatory in the UK?
Not as a standalone legal requirement. The FCA does not propose to mandate the production of a transition plan — it treats that as a matter for Government — but under CP26/5 it proposes requiring listed companies to disclose whether they have published a transition plan and where it can be found [6]. In practice, transition-plan disclosure is arriving through UK SRS S2 rather than through a separate mandate.
Does CSRD make sustainability reporting mandatory for UK companies?
Not domestically. CSRD is EU law and was never transposed into UK law. A UK-headquartered group is caught only through EU presence — under the Article 40a third-country route, where EU net turnover exceeds €450 million in each of the last two consecutive financial years and the group has a large EU subsidiary or an EU branch above €200 million turnover, reporting from financial year 2028 [7]. Most UK companies fall under UK SRS, SECR and ESOS instead.
What happens if a company does not comply?
The consequences are regime-specific. SECR and climate-disclosure obligations sit in the directors’ report or strategic report under the Companies Act 2006, so failures are company-law breaches with director responsibility [1] [3] [8]. ESOS is enforced by the Environment Agency, which can impose civil penalties for missing audits or notification [4]. See our ESOS penalties guide for the enforcement detail.
Authority sources
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Related guides & references
ESG Reporting Requirements UK
Every mandatory UK reporting regime in one reference — who reports, against what, and by when.
Is SECR Mandatory?
Whether SECR energy and carbon reporting applies to your company, and the exemptions.
Is ESOS Mandatory?
The qualification tests for mandatory ESOS energy audits under Phase 4.
Voluntary Reporting under UK SRS
Why companies adopt UK SRS before it is mandatory, and how to start.