ESOS, SECR, and UK SRS S2 are three separate UK regulatory regimes covering energy use and carbon emissions.
Large UK organisations may be in scope of all three. ESOS Phase 4 (Energy Savings Opportunity Scheme) qualifies organisations on 31 December 2026 with a compliance deadline of 5 December 2027. SECR (Streamlined Energy and Carbon Reporting) applies on an ongoing annual basis through the Directors' Report.
UK SRS S2 (Climate-related Disclosures) is proposed to apply to in-scope listed issuers from 1 January 2027 under FCA Consultation Paper CP26/5.

The three regimes have different regulators, different scopes, and different outputs — but they draw on substantially the same underlying energy and emissions data.
The UK government's Department for Energy Security and Net Zero (DESNZ) has indicated it will review the interaction between UK SRS and SECR to reduce unnecessary duplication, but no rationalisation has been confirmed and organisations should plan for full compliance with all three regimes separately.

The three regimes at a glance

Each regime has a different statutory basis, a different regulator, and a different reporting cadence. The substantive overlap is in the underlying data: energy consumption, Scope 1 and Scope 2 emissions, and (for SECR quoted companies and UK SRS S2) Scope 3 emissions.

Who is in scope of which regimes

Most large UK organisations end up in scope of more than one regime. The three common scenarios:

ESOS only. Large UK undertakings that meet ESOS thresholds (250+ employees, or annual turnover above £44m AND balance sheet total above £38m) but are not in scope of SECR or UK SRS.
This is unusual — most ESOS qualifiers also meet SECR thresholds. Example: an unlisted private group with significant industrial energy use that meets the 250-employee test but not the SECR "large company" definition.

ESOS and SECR. Large UK companies and LLPs that meet both regimes' thresholds. This is the most common position for large unlisted UK companies.
Obligations: an annual SECR disclosure in the Directors' Report plus an ESOS audit and compliance notification every four years.

ESOS, SECR, and UK SRS S2. In-scope listed issuers (UKLR 6, 14, 15, 16, 22) that also meet ESOS and SECR thresholds.
Obligations: UK SRS S2 climate disclosure in the annual financial report (from accounting periods beginning 1 January 2027, subject to the FCA's final policy statement), annual SECR in the Directors' Report, and a four-yearly ESOS audit. Example: a FTSE 350 commercial company with significant UK operations.

Quoted companies have additional SECR requirements: global Scope 1 and Scope 2 emissions disclosure, rather than just UK energy use.

ESOS Phase 4 — qualification, thresholds, and timeline

ESOS Phase 4 is the fourth four-year compliance cycle of the Energy Savings Opportunity Scheme, established by SI 2014/1643 under the EU Energy Efficiency Directive and retained in UK law post-Brexit.

Qualification date: 31 December 2026. An organisation's status on this single date determines whether it is in scope of Phase 4. Previous-phase non-qualification does not carry over — the test must be assessed afresh.

Thresholds (a UK undertaking is a "large undertaking" if):

• It employs 250 or more people, OR
• It has annual turnover above £44 million AND annual balance sheet total above £38 million (both financial tests must be met — meeting only one is not sufficient)

If any UK undertaking within a corporate group meets the threshold, all other UK undertakings in that group are in scope. The group definition follows the Companies Act 2006, capturing parent, subsidiary, and sister subsidiary undertakings.

Compliance period: 6 December 2023 to 5 December 2027. The "responsible undertaking" must submit a notification of compliance to the Environment Agency (or devolved equivalent) by 5 December 2027.

Compliance routes (Phase 4):

• An ESOS-compliant energy audit overseen by an approved Lead Assessor (the standard route)
• ISO 50001 certification covering 100% of the organisation's significant energy consumption (the alternative route)
• Display Energy Certificates (DECs) and Green Deal Assessments (GDAs) have been removed as compliance routes in Phase 4 — a significant change from Phase 3

Penalties: Civil penalties of up to £50,000 plus £500 per day for continued non-compliance, under the ESOS Regulations 2014. The Environment Agency was actively enforcing Phase 3 compliance from 2024 onwards, including against organisations that filed late or filed incomplete notifications.

ESOS Action Plans and Progress Updates

ESOS Phase 3 introduced mandatory Action Plans and Annual Progress Updates — a significant reform that carries through into Phase 4.

Phase 3 Action Plan timeline (relevant to current obligations):

• Phase 3 Action Plan submission: originally 5 December 2024, extended to 5 March 2025 due to delays in the MESOS (Manage your Energy Savings Opportunity Scheme) portal
• Phase 3 Action Plan Progress Update 1: 5 December 2025 (covering the period 6 December 2024 – 5 December 2025)
• Phase 3 Action Plan Progress Update 2: 5 December 2026 (covering the period 6 December 2025 – 5 December 2026)

Phase 4 timeline (sequencing forward):

• Phase 4 compliance notification: 5 December 2027
• Phase 4 Action Plan: 5 December 2028
• Phase 4 Annual Progress Update 1: 5 December 2029
• Phase 4 Annual Progress Update 2: 5 December 2030

The Action Plan must set out: steps to reduce energy consumption; implementation timelines; recommendations from the ESOS audit; expected energy savings over four years; and the methods used to estimate those savings. Annual Progress Updates report on actual implementation and energy savings achieved.

All Action Plans and Progress Updates are submitted via the MESOS portal and made publicly available by the Environment Agency. Where an organisation chooses not to submit an Action Plan or Progress Update, the Environment Agency publishes that the organisation does not intend to carry out energy-saving actions — a reputational consequence that did not exist in Phase 1 or Phase 2.

SECR — Streamlined Energy and Carbon Reporting

SECR was introduced by The Companies (Directors' Report) and Limited Liability Partnerships (Energy and Carbon Report) Regulations 2018 (SI 2018/1155), amending the Companies Act 2006 (particularly section 414CB) to require energy and carbon reporting in the Directors' Report or LLP Energy and Carbon Report.

Who is in scope:

• Quoted companies — all UK-listed companies of any size, with additional requirements covering global Scope 1 and Scope 2 emissions
• Large unquoted UK companies and LLPs — those meeting at least two of three criteria in two consecutive years: annual turnover above £36 million; balance sheet total above £18 million; or 250+ employees
• Large parent companies — must include consolidated group information where consolidated accounts are prepared

The "two of three" test is important: meeting just one criterion does not trigger SECR. The thresholds are set under the Companies Act 2006 size classifications.

What must be reported:

• UK energy use (gas, electricity, transport fuel) for the reporting period in kWh
• Scope 1 and Scope 2 emissions (Scope 1 globally; Scope 2 globally for quoted companies, UK-only for unquoted)
• At least one intensity ratio (such as emissions per £m turnover or per unit of production)
• Methodology used to calculate the figures
• Narrative on energy efficiency measures taken during the reporting period
• Prior-year comparatives (from the second year of reporting)
• Voluntary Scope 3 disclosure is permitted but not required

De minimis exemption: Organisations consuming less than 40 MWh of energy across the UK during the reporting period may claim a de minimis exemption from quantitative reporting. The exemption must be explicitly stated in the Directors' Report.

UK SRS S2 — the climate disclosure standard

UK SRS S2 is the UK-endorsed version of IFRS S2 — Climate-related Disclosures, published by the Department for Business and Trade on 25 February 2026. It is available for voluntary use by any UK entity. The FCA's Consultation Paper CP26/5, published 30 January 2026 and closed 20 March 2026, proposes mandatory application for in-scope listed issuers in five UK Listing Rules categories (UKLR 6 Commercial companies; UKLR 14 Secondary listings; UKLR 15 Depositary receipts; UKLR 16 Non-equity shares; UKLR 22 Transition category) from accounting periods beginning on or after 1 January 2027.

Under CP26/5:

• UK SRS S2 climate disclosures would be mandatory, with Scope 3 emissions on a comply-or-explain basis and an optional one-year deferral
• Wider sustainability disclosures under UK SRS S1 would apply on a comply-or-explain basis with an optional two-year deferral
• In-scope companies must state whether and where a transition plan has been published, and whether voluntary assurance has been obtained
• No mandatory transition plan or mandatory assurance is proposed at this stage

The first mandatory UK SRS S2 reports would be published in spring 2028 for entities with December 2027 year-ends. A final FCA Policy Statement is expected in autumn 2026.

The data overlap — same meters, different outputs

The three regimes draw on substantially the same underlying energy and emissions data, but require different presentations:

The practical implication: an organisation in scope of all three regimes that builds three separate data infrastructures will be collecting the same meter readings, fuel invoices, and emission factors three times. An organisation that builds one integrated infrastructure and outputs three regime-specific reports will save significant cost and reduce reporting error.

Where DESNZ has signalled rationalisation

The UK government's response to the UK SRS consultation, published by DBT on 25 February 2026, included an explicit commitment to consider how SECR interacts with UK SRS:

"DESNZ will consider how energy and emissions data reported by an entity using UK SRS interacts with the SECR requirements, with a view to reducing unnecessary duplication where possible."

What has been signalled:

• Recognition that UK SRS S2 and SECR cover overlapping data and create duplicative reporting
• DESNZ commitment to "consider" the interaction with a view to reducing duplication "where possible"
• Acknowledgement that large companies will be in scope of both regimes
• Recognition that ESOS, SECR, and TCFD-aligned reporting are all candidates for streamlining under the wider Modernising Corporate Reporting (MCR) programme

What has not been decided:

• Whether ESOS will be included in any rationalisation review (the explicit DESNZ commitment names SECR but not ESOS)
• Timeline for any changes to reporting requirements
• Whether formal cross-referencing between regimes will be permitted, and how
• Whether the SECR provisions in sections 414CA and 414CB of the Companies Act 2006 will be amended or repealed
• The interaction with the FCA's Listing Rules and the proposed CP26/5 mandatory regime

Planning assumption: Until further guidance is published, organisations should plan for full compliance with all three regimes separately. Any rationalisation is likely to be incremental and take several years to implement.

Section 463 Companies Act 2006 — the safe harbour for sustainability disclosure

Where UK SRS disclosures are included in the Strategic Report, the protective provisions of section 463 of the Companies Act 2006 automatically apply. Section 463 is a liability limitation for directors, not a source of additional liability — a point sometimes misreported.

Under section 463, a director is only liable to compensate the company for an untrue or misleading statement in (or omission from) the Strategic Report or Directors' Report where the director:

• Knew the statement to be untrue or misleading, or was reckless as to whether it was untrue or misleading, or
• Knew the omission to be a dishonest concealment of a material fact

The DBT consultation response confirmed that this safe harbour applies to UK SRS disclosures included in the Strategic Report, providing welcome clarity for directors of in-scope companies. The same protection does not automatically extend to disclosures published outside the Strategic Report — companies should consider where they locate UK SRS disclosures for this reason.

The 2026–2027 timing pressure

UK SRS S2 is proposed mandatory from January 2027, just under a year before the ESOS Phase 4 compliance deadline on 5 December 2027. Organisations in scope of both face a compressed window:

2026 preparation year:

• 5 December 2026 — Phase 3 ESOS Action Plan Progress Update 2 deadline
• 31 December 2026 — ESOS Phase 4 qualification date
• Throughout 2026 — UK SRS S2 preparation and voluntary application; SECR continues annually
• Autumn 2026 — FCA Policy Statement on CP26/5 expected (confirming or amending mandatory listed-issuer scope and timeline)
• 15 December 2026 — ISSA (UK) 5000 sustainability assurance standard becomes effective

2027 compliance year:

• 1 January 2027 — UK SRS S2 proposed mandatory for in-scope listed issuers (for accounting periods beginning on or after this date)
• Throughout 2027 — ESOS Phase 4 audits conducted with Lead Assessors
• 5 December 2027 — ESOS Phase 4 compliance notification deadline
• SECR continues with annual Directors' Report inclusion

2028 first reports year:

• Spring 2028 — First mandatory UK SRS S2 reports published (for December 2027 year-ends)
• Scope 3 transition relief ends under CP26/5 proposals (Scope 3 then comply-or-explain ongoing)
• 5 December 2028 — Phase 4 Action Plan deadline

The risk for in-scope organisations is sequential rather than simultaneous reporting deadlines, with overlapping data requirements but separate compliance teams. Building integrated data infrastructure in 2026 is the single most effective preparatory action.

Managing all three regimes with one data infrastructure

Most large UK organisations approach ESOS, SECR, and UK SRS as separate compliance projects with separate teams, separate consultants, and separate datasets. A more efficient approach treats them as different outputs from one underlying data infrastructure:

Common data foundation

• Energy consumption data: meter readings, supplier invoices, calculated consumption by fuel type and site. Required for all three regimes; the granularity required by ESOS audits is the most demanding and naturally satisfies SECR and UK SRS needs.
• Scope 1 and Scope 2 emissions: calculated from energy data using published emission factors (UK GHG Conversion Factors for Company Reporting, updated annually by DBT/DESNZ). Core requirement across ESOS, SECR, and UK SRS S2.
• Organisational boundaries: financial control, operational control, or equity share methodologies. Consistency across regimes is recommended but not strictly required; document any differences explicitly.
• Baseline and historical data: ESOS audits need 12 months of continuous data within the qualification period; SECR requires annual data with prior-year comparatives; UK SRS S2 requires trend disclosure under cross-industry metrics.

Regime-specific outputs

• ESOS Phase 4: energy audit report and Action Plan, submitted via MESOS portal four-yearly. Lead Assessor sign-off required. Includes energy efficiency opportunities and business case analysis.
• SECR: Directors' Report disclosure, filed annually with statutory accounts. Includes energy figures, methodology note, and energy efficiency narrative.
• UK SRS S2: climate-related financial disclosure in the annual financial report (Strategic Report or equivalent), annually. Four-pillar framework: governance, strategy, risk management, metrics and targets. Includes Scope 1, 2, and 3 emissions; scenario analysis; targets; and (for financial institutions) financed emissions.

How ESOS data feeds UK SRS S2 disclosures

The energy audit data collected for ESOS supports several UK SRS S2 requirements directly:

The reverse flow also works: UK SRS S2 scenario analysis (paragraph 22) can inform ESOS audit scoping by identifying which sites, processes, or assets are most exposed to transition risks and therefore where energy efficiency measures will have the greatest financial impact.

Practical recommendations

If you are in scope of ESOS Phase 4 only:

1. Confirm qualification at 31 December 2026 — assess group structure including joint ventures and complex ownership
2. Engage a Lead Assessor or maintain ISO 50001 certification covering 100% of significant energy consumption
3. Begin or refresh energy data collection covering the 12-month audit reference period
4. Identify and cost energy efficiency opportunities; prepare Action Plan content (mandatory in Phase 4)
5. Submit compliance notification via MESOS portal by 5 December 2027
6. Submit Phase 4 Action Plan by 5 December 2028

If you are in scope of ESOS and SECR:

1. Complete all ESOS Phase 4 steps above
2. Ensure SECR annual disclosure in the Directors' Report uses the same underlying energy data, with appropriate methodology disclosure
3. Track Companies Act 2006 size threshold changes — the 2025 increases did not change SECR thresholds, but future amendments could
4. Document organisational boundaries consistently across both regimes

If you are in scope of all three regimes:

1. Complete ESOS and SECR steps as above
2. Map existing TCFD-aligned disclosures against UK SRS S2 requirements (paragraphs 5–37); identify gaps in governance, strategy, risk management, metrics, and targets
3. Begin or upgrade climate scenario analysis to meet UK SRS S2 paragraph 22 — consider NGFS and IEA scenarios
4. Begin Scope 3 emissions data infrastructure (supplier engagement is the long-lead-time work); use CP26/5 one-year transition relief if needed
5. Engage assurance providers early for ISSA (UK) 5000 scoping
6. Build governance integration across sustainability, finance, risk, legal, and operations functions
7. Monitor the FCA Policy Statement (autumn 2026) for confirmed scope and timeline

For all organisations regardless of regime:

• Treat ESOS Action Plan content as a regulatory commitment, not a paper exercise. Phase 4 requires explanation of unmet commitments and ties progress reporting to compliance status
• Use the same emission factors and organisational boundaries across all reports unless there is a specific reason not to. Inconsistency triggers assurance queries and reduces report credibility
• Plan for assurance readiness even where assurance is not currently mandatory. The direction of travel under ISSA (UK) 5000 and FCA proposals is towards mandatory assurance over time