ESOS compliance guidance — how to comply, step by step
Complying with the Energy Savings Opportunity Scheme means qualifying, auditing at least 95% of your energy consumption, obtaining lead assessor and board sign-off, and notifying the Environment Agency by 5 December 2027.
This guide covers every step, deadline and penalty.
Two dates decide everything
This ESOS compliance guidance comes down to two questions — was any UK entity in your group a large undertaking on 31 December 2026, and has the Environment Agency heard from you by 5 December 2027?
Large means 250+ UK employees — tap it — and between those two dates sits the actual work: measuring your energy, auditing at least 95% of it (or covering it with ISO 50001), and getting a director to sign.
The official guidance is the Environment Agency’s ESOS guidance on GOV.UK, under SI 2014/1643 as amended in 2023 — this page puts it in working order.
Nobody told the subsidiary
A distribution firm in the Midlands — 140 staff, well under every threshold it has ever checked.
In 2025 its parent group bought a warehousing business, and on 31 December 2026 the group’s UK headcount stands at 320.
ESOS uses group aggregationIf the highest UK parent or any UK group entity meets the large-undertaking test on the qualification date, the entire UK corporate group is in scope — and it keeps qualifying until it fails the test for two consecutive accounting periods. — so the whole group is now in scope, and nobody in the subsidiary knows.
The finance director finds out in September 2027, with 0 working days left to measure a year of energy, audit 95% of it, and get an assessor and a director to sign.
Lead assessor capacity tightens in the final year of every phase — the queue forms exactly when she needs it not to.
The penalties are civil, published, and per breach
The Environment Agency enforces ESOS with civil penalties under regulation 29 of SI 2014/1643.
Failing to undertake an energy audit carries an initial penalty of up to £50,000.
Failing to notify, or to keep records, carries up to £5,000 — plus up to £500 per working day of continued breach, capped at 80 working days.
Every penalty also carries a publication penalty: the breach, and your organisation’s name, on a public register.
The Agency starts from the statutory maximum and adjusts for culpability, size, history and cooperation — the stepped approach in Annex 2 of its enforcement and sanctions policy.
Compliance is a four-year rhythm, not a filing
Each phase fixes a 31 December qualification date, allows roughly a year to assess, and closes with a 5 December notification — and since the 2023 amendment, the years in between carry action-plan progress updates too.
So — does any of this actually bind you?
The qualification test, on your figures
On 31 December 2026, an organisation is in scope if it has 250 or more UK employees, or turnover above £44 million and a balance sheet above £38 million — both.
Group aggregation means one qualifying UK entity puts the whole UK group in scope.
This is not the SECR test — SECR uses two-of-three at £36m / £18m / 250 — so check each independently.
Public bodies are generally out of scope.
One number, two routes to cover it
However you comply, at least 95% of your total energy consumption — buildings, transport, industrial processes — must be covered.
An ESOS energy audit is the standard route; a certified ISO 50001 energy management system is a full alternative for whatever consumption it covers.
Cover everything with ISO 50001 and no lead assessor review is required at all — you simply notify.
The remaining ≤5% is the de minimis exclusion — the one part of your consumption the scheme lets you leave unexamined.
First things first — and why first
Allow 12–18 months for the full cycle — the order below exists because each step feeds the next.
If any UK entity in your group was large on 31 December 2026, the Environment Agency must hear from you by 5 December 2027 — with 95% of your energy audited behind the notification.
You understand what ESOS asks. The audit is where the work — and the worth — actually lives.
See what the energy audit involves Or make the data pay twice — ESOS into UK SRS S2ESOS compliance guidance — the essentials
ESOS — the Energy Savings Opportunity Scheme — is the UK’s mandatory energy assessment scheme for large undertakings, established by the ESOS Regulations 2014 (SI 2014/1643) and administered by the Environment Agency.
If you are new to the scheme itself, start with the ESOS overview — this page is the practical ESOS compliance guidance: who qualifies, what you must do, by when, and what it costs to get it wrong.
The canonical official guidance is the GOV.UK ESOS guidance, maintained by the Environment Agency and DESNZ.
Read it alongside the ESOS (Amendment) Regulations 2023 (SI 2023/1182), which raised audit coverage to 95% and added the Part 6A action plan and progress-update obligations that now run between phases.
In Scotland, Wales and Northern Ireland the scheme is administered by SEPA, Natural Resources Wales and NIEA respectively.
Who must comply — the qualification criteria
An organisation is in scope if, on the qualification date (31 December 2026 for Phase 4), it is a UK large undertaking: it has 250 or more employees, or it has annual turnover above £44 million and a balance sheet total above £38 million.
Group aggregation extends the net: if any single UK entity in a corporate group meets either test, the entire UK group must comply.
An undertaking keeps its qualifying status until it fails the test for two consecutive accounting periods.
The ESOS test differs from SECR’s two-of-three test (£36m turnover / £18m balance sheet / 250 employees), so an organisation can be caught by one regime and not the other — check each independently.
Public bodies are generally outside ESOS — see ESOS exemptions for who falls out of scope and the edge cases around groups, franchises and trusts.
The six compliance requirements
Six obligations make up full compliance — from measuring total energy consumption to the action plan and progress updates that follow notification.
Calculate total energy use across buildings, transport and industrial processes for a 12-month period that includes the qualification date.
This total defines the 95% that must be covered by audits or ISO 50001.
Cover at least 95% of total energy consumption through ESOS-compliant energy audits, ISO 50001 certification, or a mixed approach.
The threshold was raised from 90% by SI 2023/1182 — the remaining ≤5% is the de minimis exclusion.
A registered lead assessor must review and sign off the assessment, unless 100% of consumption is covered by ISO 50001 or total energy use is below 40,000 kWh a year.
A board-level director must review the assessment and confirm compliance before the notification is submitted — a personal, named accountability step.
Submit the compliance notification through the Environment Agency’s Manage your ESOS reporting (MESOS) service by the phase deadline — 5 December 2027 for Phase 4.
See the full notification guide for what the submission must contain, and how a Do Not Qualify (DNQ) notification differs.
Under Part 6A (inserted by SI 2023/1182), participants must submit an ESOS action plan after notification and follow it with board-signed annual progress updates — turning ESOS from a one-off audit into a continuous obligation between phases.
How to comply with ESOS
Five steps take a qualifying organisation from the qualification test to a submitted notification — allow 12–18 months for the full cycle.
Most organisations comply through a full ESOS energy audit of their highest-consuming sites, sampling the rest.
A certified ISO 50001 energy management system is an alternative route for the consumption it covers — and if it covers 100%, no lead assessor review is needed at all; see ISO 50001 vs ESOS for how to choose between the two routes.
The GOV.UK guidance also recognises a mixed approach, and the Environment Agency’s step-by-step “Comply with ESOS” publication sets out what each route has to evidence.
Whichever route you choose, start early: lead assessor capacity tightens in the final year of every phase, and the Phase 4 compliance guide sets out a realistic 18-month countdown to the deadline.
For structured templates for the action plan and evidence pack, see ESOS templates.
Complying with the Energy Savings Opportunity Scheme
Complying with the Energy Savings Opportunity Scheme means working to its four-year phase cycle — qualification, assessment, notification, then action plan and progress updates.
Each phase fixes a 31 December qualification date, allows roughly a year for assessment, and closes with a 5 December notification deadline.
Since SI 2023/1182, the years between notifications are no longer quiet: the action plan and its annual progress updates keep participants reporting continuously.
Phase 3 participants, for example, still owe a progress update on 5 December 2026 — the same month as the Phase 4 qualification date.
ESOS compliance deadlines
Two Phase 4 dates matter most: the qualification date of 31 December 2026 and the notification deadline of 5 December 2027.
The qualification date follows the four-yearly cycle set by SI 2014/1643, whose Schedule 1 carries the large-undertaking test, and the deadline is confirmed in the GOV.UK ESOS guidance.
Working back from 5 December 2027, assessor appointment and data scoping should start by mid-2026.
Every active date — including the Phase 3 progress updates running in parallel — is tracked on our ESOS deadlines page.
Penalties for non-compliance
The Environment Agency applies the civil penalties set out in regulation 29 of SI 2014/1643 using the stepped approach in Annex 2 of its enforcement and sanctions policy — starting from the statutory maximum, then adjusting for culpability, organisation size, history and cooperation.
The statutory maxima include an initial penalty of up to £50,000 for failing to undertake an energy audit, up to £5,000 for failing to notify or to maintain records, and daily penalties of up to £500 per working day, capped at 80 working days, for continued breach.
Every penalty carries a publication penalty: the breach is published on a public register.
For organisations that also report under UK SRS or SECR, a named ESOS failure sits uncomfortably next to voluntary sustainability claims — procurement teams and investors increasingly check the register.
Alongside SECR and UK SRS
ESOS compliance work does not exist in isolation — the same energy data flows up the stack.
The consumption data gathered for the audit underpins annual SECR disclosures in the directors’ report, and for listed companies it is a natural evidence source for Scope 1 and 2 emissions under UK SRS S2 — see how ESOS energy data feeds into UK SRS S2 for the practical mapping.
The DESNZ GHG conversion factors (2026) are the common currency across all three regimes.
Aligning the three reporting cycles reduces duplication and keeps one consistent energy dataset across every regime.
ESOS compliance guidance — frequently asked questions
ESOS compliance means meeting the obligations of the Energy Savings Opportunity Scheme — the UK’s mandatory energy assessment scheme for large undertakings, administered by the Environment Agency under the ESOS Regulations 2014 (SI 2014/1643). Qualifying organisations must measure their total energy consumption, have at least 95% of it audited (or covered by ISO 50001), obtain lead assessor and board director sign-off, and notify the Environment Agency via the MESOS portal every four-year phase.
Any UK large undertaking must comply: an organisation with 250 or more employees, or one with annual turnover above £44 million and a balance sheet total above £38 million, assessed on the qualification date (31 December 2026 for Phase 4). Group aggregation applies — if any UK entity in a corporate group meets the test, the whole UK group is in scope. Public bodies are generally out of scope.
Five steps: (1) confirm qualification against the large undertaking test on the qualification date; (2) measure total energy consumption across buildings, transport and industrial processes; (3) cover at least 95% of that consumption through ESOS-compliant energy audits, ISO 50001 certification, or a mix of the two; (4) have a registered lead assessor review the assessment and a board-level director sign it off; (5) submit the compliance notification to the Environment Agency through the MESOS service by the phase deadline, then deliver the action plan and annual progress updates that follow.
The Phase 4 qualification date is 31 December 2026 and the compliance notification deadline is 5 December 2027. Organisations that qualify on 31 December 2026 must complete their assessment and notify the Environment Agency via MESOS by 5 December 2027.
The Environment Agency enforces ESOS through civil penalties using the stepped approach in Annex 2 of its enforcement and sanctions policy. Statutory maxima under the ESOS Regulations 2014 include an initial penalty of up to £50,000 for failing to undertake an energy audit, up to £5,000 for failing to notify, daily penalties of up to £500 per working day (capped at 80 working days), and a publication penalty naming the organisation on a public register.
Yes. A certified ISO 50001 energy management system is a full ESOS compliance route for the energy consumption it covers. If ISO 50001 certification covers 100% of your energy use, no lead assessor review is required — you simply notify the Environment Agency. Partial ISO 50001 coverage can be combined with ESOS energy audits to reach the 95% threshold.
Explore the ESOS guides
Dedicated pages covering every stage of the compliance journey.
ESOS — scheme overview
What ESOS is, who qualifies and how the phases work.
Phase 4ESOS Phase 4 compliance guide
Qualification checker, what changed from Phase 3, and the 2027 deadline.
Action plansESOS action plan guide
Part 6A action plans, annual progress updates and MESOS submission.
Lead assessorAppointing a lead assessor
Approved registers, qualifications and how to brief an assessor.
ScopeESOS exemptions
Public bodies, de-qualification and the group-structure edge cases.
DeadlinesESOS deadlines — all phases
Every Phase 3 and Phase 4 date in one tracker.
Where to go next
ESOS — the Energy Savings Opportunity Scheme
What ESOS is, why it exists and who runs it — the section hub.
Phase 4ESOS Phase 4 compliance guide
Qualification on 31 Dec 2026, the 95% coverage rule and the 5 Dec 2027 deadline.
Action plansESOS action plan — requirements and deadlines
The Part 6A action plan and annual progress update obligations.
AuditsESOS energy audit requirements
12-month data requirements, site visits and audit methodology.
IntegrationESOS and UK SRS S2
How ESOS energy data feeds UK SRS S2 climate disclosures.
Primary sources
Every figure and legal statement on this page carries an inline citation. These are the primary documents behind them.