ESOS legislation · legal force
Is ESOS mandatory
ESOS is mandatory for every large undertaking and its UK group under the ESOS Regulations 2014, and the sanctions are civil penalties set in the Regulations themselves.
Not every duty carries one: the notification, the records and the assessment do, and the action plan and progress updates do not.
This page reads the ESOS legislation for its force: the power behind it, what each duty risks, and what is voluntary.
The short answer
Mandatory for large undertakings, enforced by civil penalty
Module 01 / 04
Notify compliance
Module 02 / 04
Keep an evidence pack
Module 03 / 04
Carry out the ESOS assessment
Module 04 / 04
Comply with a notice
| Duty | Compulsory? | Sanction |
|---|---|---|
| Notify compliance | Yes | reg 43 |
| Keep an evidence pack | Yes | reg 44 |
| Carry out the ESOS assessment | Yes | reg 45 |
| Comply with a notice | Yes | reg 46 |
| Produce an action plan | Yes | None in Part 8 |
| File progress updates | Yes | None in Part 8 |
| Include net zero | No | — |
Read the detailed guidance and evidence
ESOS reporting is mandatory: a relevant undertaking must carry out an ESOS assessment and notify the scheme administrator that it has complied, by the compliance date.
An undertaking meets the numerical size condition if it employs at least 250 persons, or has both turnover over £44 million and a balance sheet over £38 million, under Schedule 1.
Size and status follow the Schedule 1 accounting-period and two-period rules. Smaller UK group undertakings can also participate through a qualifying member, subject to regulation 15, the exclusions in regulation 16 and the Schedule 1 status-history rules; regulation 17 has the group comply as one participant.
The consequences are the civil penalties in Part 8 and the publication of the penalty.
Two duties sit outside that table: the action plan and the progress updates are required, but nothing in Part 8 penalises missing them.
The qualification test in detail is on ESOS Phase 4 thresholds.
ESOS legislation
The legal basis, from a Directive to an Act
Module 01 / 04
SI 2014/1643
Module 02 / 04
SI 2023/1182
Module 03 / 04
SI 2026/701
Module 04 / 04
Legal route
| Instrument | Power |
|---|---|
| SI 2014/1643 | European Communities Act 1972 s.2(2) |
| SI 2023/1182 | Energy Act 2023 ss.254–260, 263 |
| SI 2026/701 | Energy Act 2023 ss.254–260, 263 |
Read the detailed guidance and evidence
The 2014 Regulations were made on 24 June 2014 by a minister designated under section 2(2) of the European Communities Act 1972, and came into force on 17 July 2014.
Their own marginal note says they transpose Article 8(4) to (6) of the Energy Efficiency Directive 2012/27/EU, the article that required energy audits of large enterprises.
That Directive was repealed in October 2025 by the 2023 recast, and is the scheme’s origin, not its authority.
The authority for changing ESOS now is the Energy Act 2023: both the 2023 amendments, made on 7 November 2023, and the 2026 amendments, made on 23 June 2026, cite sections 254 to 260 and 263.
SI 2023/1182 brought in the Phase 3 changes, including action plans and the 95% coverage line.
SI 2026/701 brought in the Phase 4 changes, from 22 July 2026.
The sterling thresholds are older than both: they replaced the euro figures for qualification dates from 31 December 2020, under the EU Exit amendments of 2018.
The sanctions
Which ESOS regulations carry a penalty
Part 8 names the duties it penalises.
Anything it does not name is a duty without a sanction of its own, however firmly it is worded.
Module 01 / 04
Notify the scheme administrator
Module 02 / 04
Keep the evidence pack
Module 03 / 04
Undertake the ESOS assessment
Module 04 / 04
Comply with a compliance, enforcement or pen
Read the detailed guidance and evidence
| Duty | Provision | Penalty | Maximum |
|---|---|---|---|
| Notify the scheme administrator | reg 29 | reg 43 | £5,000 + £500 per working day, up to 80 — £45,000 |
| Keep the evidence pack | reg 28 | reg 44 | £5,000 + the cost of confirming compliance |
| Undertake the ESOS assessment | Part 4 | reg 45 | £50,000 + £500 per working day, up to 80 — £90,000 |
| Comply with a compliance, enforcement or penalty notice | regs 35, 38, 39 | reg 46 | £5,000 + £500 per working day, up to 80 |
| Make no false or misleading statement | — | reg 47 | £50,000 |
| Produce an action plan | reg 34A | — | None |
| File progress updates | reg 34B | — | None |
The daily element runs per working day, capped at 80, which the Environment Agency’s guidance sometimes writes without the word “working”.
Regulation 45 was narrowed by SI 2026/701 so that it does not bite where the ISO 50001 route or the zero-energy route applies.
The gap for action plans is in the statute, not only in policy, and the Environment Agency confirms it will not take enforcement action for non-submission, publishing the failure instead.
The one route back to a sanction is regulation 46: an enforcement notice requiring a plan could be enforced if ignored.
How the Agency sets an amount inside those maxima is in its enforcement policy, Annex 2, and worked through on ESOS penalties.
For a first-time participant that fails to undertake the audit, the annex says the Agency will normally cap the initial penalty at £5,000, in that first compliance period only.
Voluntary
What ESOS does not compel
Module 01 / 04
Key point 01
Module 02 / 04
Proposal
Module 03 / 04
Voluntary route
Module 04 / 04
Legal route
A net zero assessment under PAS 51215-1:2025 is optional in Phase 4.
MESOS does not accept voluntary decarbonisation assessments, so a participant that does one publishes it itself.
Read the detailed guidance and evidence
ESOS does not require a participant to implement any measure it identifies.
An action plan can be a statement that no measure is proposed, under regulation 34A(3)(b).
It does not require net zero assessment: the GOV.UK ESOS overview says Phase 4 participants may include it voluntarily using PAS 51215-1:2025 and PAS 51215-2:2025.
The competence standard for ESOS lead assessors remains PAS 51215:2014, fixed by regulation 12, though BSI lists that edition as withdrawn.
It does not require a management system: an ISO 50001 certificate is one route, not a duty, covered on ISO 50001 and ESOS.
An organisation under the thresholds may carry out an ESOS assessment voluntarily, but cannot notify it, because MESOS takes no submissions from voluntary participants.
The voluntary side of the standards world is set out on voluntary reporting under UK SRS.
Enforcement
Who enforces ESOS, and how many comply
Module 01 / 04
Key point 01
Module 02 / 04
Key point 02
Module 03 / 04
Boundary
Module 04 / 04
Boundary · 2
Read the detailed guidance and evidence
Enforcement follows the registered office: the Environment Agency in England, Natural Resources Wales, SEPA in Scotland and the Northern Ireland Environment Agency, with the Secretary of State for offshore undertakings.
The Environment Agency is also the scheme administrator for the whole UK, and publishes the guidance on behalf of all of them.
The second post-implementation review counted 8,581 groups that notified for Phase 3, against 9,871 the Agency believed qualified.
It also counted 5,403 action plans among those groups, which is the practical effect of a duty with no penalty behind it.
The review calls the figures provisional, because notifications and plans were still arriving as enforcement continued.
The Phase 4 guidance itself is the Environment Agency’s publication of 30 July 2026.
Compared
ESOS against the other energy and climate duties
Module 01 / 04
ESOS
Module 02 / 04
SECR
Module 03 / 04
FCA listing rules
Read the detailed guidance and evidence
| Regime | Compels | Source of the duty | Status |
|---|---|---|---|
| ESOS | A four-yearly energy assessment and notification | SI 2014/1643 | Mandatory for large undertakings |
| SECR | Annual energy and carbon disclosure in the directors’ report | SI 2008/410 Sch 7 | Mandatory for quoted, and for large unquoted companies and LLPs |
| FCA listing rules | Reporting against UK SRS, or an explanation | PS26/19 | Comply or explain, accounting periods from 1 Jan 2027 |
| UK SRS S1 and S2 | Nothing by themselves | DBT, 25 February 2026 | Voluntary standards |
Mandatory means different things across these regimes, and the difference is who can penalise you.
An ESOS failure is a civil penalty from the environmental regulator; a SECR disclosure sits in the annual report and is monitored as part of it.
The FCA’s final rules make UK SRS a comply-or-explain obligation for listed companies in scope, which is not the same as mandatory: an explanation of why not is compliance.
Section 463 of the Companies Act 2006 limits directors’ liability for statements in the strategic and directors’ reports; an ESOS notification is a filing with the regulator, not a report under that section.
The SECR comparison is on ESOS vs SECR and SECR and UK SRS, and the shared data on ESOS and UK SRS.
The other side
Where UK SRS is voluntary, and where it is not
Module 01 / 04
Listed categories
Module 02 / 04
Deadline
Module 03 / 04
Standard
Module 04 / 04
Scope 3
Read the detailed guidance and evidence
UK SRS is often described as mandatory in the same breath as ESOS, and it is not: the UK SRS standards are voluntary, and the FCA’s rules apply comply or explain to listed companies.
Which companies that reaches is on UK SRS scope, the dates on the UK SRS timeline, the S1 and S2 timeline and UK SRS deadline.
The two standards are explained on UK SRS S1 and UK SRS S2, and their structure on the four pillars.
The hardest disclosure is on Scope 3 under UK SRS, the forward-looking one on transition plans, and the separate assurance position for UK SRS disclosures on UK SRS assurance.
How the standards compare with older frameworks is on UK SRS vs TCFD and UK SRS vs CSRD.
For implementation, see UK SRS compliance, UK SRS for boards, UK SRS for financial services and the UK SRS FAQ.
The wider activity is described on sustainability reporting, and on the ESOS side the audit is on ESOS energy audits and the plan on the ESOS action plan.
Frequently asked
Is ESOS mandatory: questions people ask
Is ESOS mandatory?
Yes, for relevant undertakings under regulations 15 and 16.
The individual large-undertaking test is at least 250 persons employed, or both turnover over £44 million and balance sheet total over £38 million, using Schedule 1 accounting-period figures and its two-period status rule.
Size and status follow the Schedule 1 accounting-period and two-period rules.
Smaller UK group undertakings can also participate through a qualifying member, subject to the statutory exclusions.
The duties are set by the Energy Savings Opportunity Scheme Regulations 2014 and enforced through civil penalties in Part 8 of those Regulations.
What is the ESOS legislation?
The Energy Savings Opportunity Scheme Regulations 2014 (SI 2014/1643), made on 24 June 2014 under section 2(2) of the European Communities Act 1972 to transpose Article 8 of the Energy Efficiency Directive.
They were amended by SI 2023/1182 from 29 November 2023 and SI 2026/701 from 22 July 2026, both made under sections 254 to 260 and 263 of the Energy Act 2023.
What penalties do companies face for non-compliance with ESOS?
Part 8 of the Regulations sets five civil penalties: failure to notify (up to £5,000 plus £500 per working day for up to 80 working days), failure to keep records (£5,000 plus the regulator's audit costs), failure to undertake an ESOS assessment (up to £50,000 plus £500 per working day for up to 80 working days), failure to comply with a notice (as for notification), and a false or misleading statement (up to £50,000). Each can also be published.
Is the ESOS action plan mandatory?
The duty is: regulation 34A requires an action plan after every notification of compliance.
But no penalty in Part 8 attaches to it, and the Environment Agency says it will not take enforcement action for non-submission; the failure is published instead.
A plan can be a statement that no measures are proposed.
Is net zero assessment mandatory under ESOS Phase 4?
No. The ESOS (Amendment) Regulations 2026 contain no net zero requirement.
The GOV.UK ESOS overview says Phase 4 participants can voluntarily include net zero considerations using PAS 51215-1:2025 and PAS 51215-2:2025, and that MESOS cannot receive a voluntary decarbonisation assessment.
Can a company below the thresholds do ESOS voluntarily?
Yes, it can carry out an ESOS-style assessment, but it cannot notify it: the Environment Agency says MESOS does not accept submissions from voluntary participants, and suggests publishing the results in the organisation's own reports or website.
Who enforces ESOS?
The regulator follows the registered office: the Environment Agency for England, Natural Resources Wales, SEPA for Scotland and the Northern Ireland Environment Agency, with the Secretary of State for offshore undertakings.
The Environment Agency is also the scheme administrator for the whole UK.
Is ESOS reporting the same as UK SRS reporting?
No. An ESOS notification is a filing with the Environment Agency under the ESOS Regulations.
UK SRS S1 and S2 are voluntary standards; listed companies in UKLR 6, 14, 15, 16 and 22 report against them on a comply-or-explain basis under the FCA's final rules for accounting periods beginning on or after 1 January 2027.
Prepare the evidence
Is ESOS mandatory: from a requirement to a reporting pack
Use this preparation sequence alongside the detailed requirements on this page.
An editorial workflow, not a statutory schedule.
- Stage 0101
Qualification record
Resolve the undertaking and group position at the qualification date.
- Stage 0202
Energy period
Retain the chosen reference period and its source records.
- Stage 0303
Assessment coverage
Document the audit coverage, exclusions and compliance routes used.
- Stage 0404
Assessor review
Check whether a lead assessor is needed for the chosen compliance route.
- Stage 0505
Approval and notification
Retain the applicable director sign-off and notification evidence.
- Stage 0606
Action plan
Use the assessment findings to support the applicable action plan and progress record.
Read the applicable instrument: The Energy Savings Opportunity Scheme Regulations 2014 (SI 2014/1643), revised text
A practical brief
An evidence pack, with a clear review trail
Ask for a pack that lets the next reviewer retrace the scope decision, follow the evidence and understand the limitations.
This describes a useful handover; it does not certify compliance or establish that a vendor or adviser delivers it.
Module 01 / 04
Applicability record
Write down the entity, reporting route and relevant period, including why the route applies.
Module 02 / 04
Evidence register
Attach each reported figure or statement to its source, method, version and limitations.
Module 03 / 04
Review trail
Name the preparer, reviewer, open questions and decisions taken before publication.
Module 04 / 04
Usable handover
Retain the working files and unresolved actions so the next reporting cycle can reuse the evidence.
View the preparation diagram
- Prepare01
Create the traceable pack
Keep the input records, calculation files and narrative together.
- Challenge02
Resolve questions before publication
Record the assumptions challenged and any limitations still unresolved.
- Retain03
Make the next cycle reproducible
Keep the approved version and the actions carried forward.
Continue your research
Related guides, one question at a time
Sources
Primary sources
Every figure, date and status on this page traces to the instrument’s owner.
Secondary commentary is never the source for a number.
- legislation.gov.ukThe Energy Savings Opportunity Scheme Regulations 2014 (SI 2014/1643), revised text
In force 17 July 2014. Consolidation of the 2026 amendments is partial — read with SI 2026/701.
- legislation.gov.ukSI 2014/1643, introductory text — made 24 June 2014 under European Communities Act 1972 s.2(2)
- legislation.gov.ukEnergy Act 2023, sections 254–260 and 263 — energy savings opportunity schemes
The power under which SI 2023/1182 (made 7 November 2023) and SI 2026/701 were made; the 2014 Regulations were made under European Communities Act 1972 s.2(2).
- legislation.gov.ukThe Energy Savings Opportunity Scheme (Amendment) Regulations 2023 (SI 2023/1182)
In force 29 November 2023: the Phase 3 changes — action plans, the 95% line, site visits, intensity ratios.
- legislation.gov.ukThe Energy Savings Opportunity Scheme (Amendment) Regulations 2026 (SI 2026/701)
Made 23 June 2026, in force 22 July 2026: the Phase 4 changes. Made under Energy Act 2023 ss.254–260 and 263.
- legislation.gov.ukESOS Regulations 2014, Schedule 1 ¶¶1, 1A, 5, 9–11 — the large undertaking test
At least 250 persons, or turnover in excess of £44m and balance sheet in excess of £38m; monthly-average headcount (¶10); two-period status rule (¶11).
- legislation.gov.ukESOS Regulations 2014, regulation 17 — participants and the highest parent group
A highest parent group complies as one participant; parent undertaking in the Companies Act 2006 s.1162 sense.
- legislation.gov.ukESOS Regulations 2014, Part 8 (regulations 39–47) — civil penalties
The five penalties and publication; regulations 34A and 34B are named nowhere in Part 8.
- legislation.gov.ukESOS Regulations 2014, Part 6A (regulations 34A–34B) — action plans and progress updates
Consolidated to 22 July 2026: contents, windows, kWh basis, the third progress update, the zero-energy carve-out.
- EUR-LexDirective 2012/27/EU — Energy Efficiency, Article 8 (mandatory energy audits). Repealed October 2025 by Directive (EU) 2023/1791; cited for ESOS's origin, not as current law.
- Environment AgencyHow to comply with the Energy Savings Opportunity Scheme (ESOS) phase 4
Published 30 July 2026. A restatement of the Regulations, never the source over them; where it and the SI differ, the SI governs.
- Environment AgencyComply with the Energy Savings Opportunity Scheme (ESOS) phase 4 — publication page
- Environment Agency / GOV.UKEnergy savings opportunity scheme (ESOS): find out if you qualify and how to comply
Rewritten for Phase 4 on 2 September 2026; seven approved lead assessor registers; PAS 51215-1 and -2:2025 voluntary.
- Environment AgencyEnforcement and sanctions policy, Annex 2: climate change schemes — civil penalties
Updated 10 October 2025. Step 3 bands and the ESOS worked example; §D2.3 new entrants.
- Department for Energy Security and Net ZeroThe ESOS Regulations 2014 — second Post Implementation Review (18 July 2025, PDF)
¶19: 9,871 groups believed to qualify for Phase 3; 8,581 notified; 5,403 action plans. Recommendation: keep.
- BSIPAS 51215-1:2025 — Energy and decarbonization assessment, Part 1: Process
Voluntary for ESOS; the regulator names PAS 51215:2014 as the lead assessor competency standard.
- ISOISO 50001 — Energy management
- legislation.gov.ukCompanies Act 2006, section 463 — liability for false or misleading statements in reports
Covers statements in the strategic, directors’ and remuneration reports — not an ESOS notification.
- legislation.gov.ukSI 2008/410 Schedule 7 Part 7A — SECR for large unquoted companies
The two-or-more exemption test; a different regime.
- Financial Conduct AuthorityPS26/19: Aligning listed issuers’ sustainability disclosures with international standards
30 September 2026: comply or explain against UK SRS for UKLR 6, 14, 15, 16 and 22.
- Department for Business and TradeUK Sustainability Reporting Standards: UK SRS S1 and UK SRS S2
Voluntary standards, published 25 February 2026.
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