ESOS Phase 4 · deadline and dates
ESOS Phase 4 deadline: every date, and a plan to meet it
The ESOS Phase 4 deadline is 5 December 2027, and the qualification date is 31 December 2026 — both generated by regulation 4 of the ESOS Regulations 2014.
This page sets out every Phase 4 date through to 2031, what each one requires, and an indicative quarter-by-quarter plan to reach the deadline.
The deadline
The ESOS Phase 4 deadline is 5 December 2027
5 December 2027 is the compliance date: the last day to notify compliance through MESOS, the Environment Agency’s notification system.
It is not a guidance date; it is generated by regulation 4(2) and 4(4)(b), which end each compliance period on 5 December four years after the last.
The Environment Agency’s Phase 4 guidance says in its penalties section that the deadline was revised by the 2026 amendment; the amending instrument does not bear that out.
Missing the date is a failure to notify under regulation 43: up to £5,000 plus £500 for each working day the failure continues, capped at 80 working days, and publication.
Failing to undertake the ESOS assessment itself (regulation 45) carries £50,000, or a lesser amount the regulator determines, plus the same daily penalty.
The full route to the notification is in the ESOS Phase 4 compliance guide, and the scheme is summarised on our ESOS Phase 4 page.
No.
SI 2026/701 does not amend regulation 4, and 5 December 2027 still follows from it.
Phase 3’s compliance date was extended by six months; Phase 4’s has not been.
Key dates
ESOS Phase 4 dates, 2022 to 2031
Every date below is either in the Regulations or derivable from them, except the audit data window, which is GOV.UK’s.
| Date | What happens | Source |
|---|---|---|
| 6 Dec 2022 | Earliest start of the 12 months of audit data for Phase 4 | GOV.UK ESOS guidance |
| 6 Dec 2023 | Phase 4 compliance period begins | Reg 4(2) |
| 6 Dec 2023 | Earliest issue date for an ISO 50001 certificate relied on in Phase 4 | EA Phase 4 guidance |
| 22 Jul 2026 | SI 2026/701 in force: the Phase 4 changes | SI 2026/701 |
| 5 Dec 2026 | Phase 3 second progress update due (if you filed a Phase 3 action plan) | Reg 34B |
| 31 Dec 2026 | Qualification date | Reg 4(3)(b) |
| 5 Dec 2027 | Compliance date: notification through MESOS | Reg 4(4)(b) |
| 5 Dec 2028 | Phase 4 action plan due | Reg 34A(7)(b), (10) |
| 5 Dec 2029 | Initial progress update due | Reg 34B(1)(a) |
| 5 Dec 2030 | Further progress update due | Reg 34B(1)(b) |
| 5 Dec 2031 | Final progress update due — new in Phase 4 | Reg 34B(1)(c) |
The action plan and progress update dates are derived from Part 6A: the relevant compliance period for Phase 4’s action plan is the one that begins on 6 December 2027.
The Environment Agency’s own guidance contradicts itself on the number of Phase 4 progress updates; the Regulations, as amended, require three.
Phase 5 follows directly: compliance period 6 December 2027 to 5 December 2031, qualification date 31 December 2030.
Qualification date
The ESOS Phase 4 qualification date
The qualification date is 31 December 2026.
An undertaking that on that day employs at least 250 people, or has an annual turnover in excess of £44 million and an annual balance sheet total in excess of £38 million, is a large undertaking for Phase 4.
If any UK undertaking in a group qualifies, the whole UK group participates.
An undertaking that was large keeps that status until it has been small or medium for two consecutive accounting periods.
Status on 31 December 2026 governs even if the organisation’s size changes afterwards.
How the thresholds interact with part-year accounts and group structures is worked through in the ESOS thresholds guide.
| Test on 31 Dec 2026 | Qualifies if |
|---|---|
| Employees | At least 250 |
| Turnover and balance sheet | In excess of £44m and in excess of £38m — both |
Requirements
ESOS Phase 4 requirements, against the dates
The ESOS Phase 4 requirements build on Phase 3, with additions from SI 2026/701.
A qualifying organisation measures its total energy consumption over a 12-month reference period.
Under regulation 22(5) that period ends on or before the compliance date, and the guidance requires it to include 31 December 2026.
It then audits its energy use, or relies on certified ISO 50001 covering its total or significant consumption; Display Energy Certificates and Green Deal Assessments are no longer routes.
A lead assessor on one of the seven approved registers carries out or reviews the assessment, unless ISO 50001 covers it or total consumption is below 40,000 kWh.
Since 22 July 2026 the lead assessor must also notify their own approval body within seven days of completing the assessment (SI 2026/701 regulation 8).
The report must now state the energy savings achieved in the period and review which previous action-plan measures were not implemented, and why.
One responsible officer confirms where the lead assessor is independent of the participant; two in any other case.
Then the organisation notifies, by 5 December 2027.
Due by 5 December 2027
- 01Total energy consumption
Four organisational purposes: transport, industrial processes, buildings, any other purpose.
- 02Audit or ISO 50001
Over total consumption, or the areas making up at least 95% if identified.
- 03Lead assessor
Carries out or reviews the assessment, unless exempt.
- 04Savings achieved, action plan review
New in Phase 4, in kWh.
- 05Responsible officer(s) confirm
One if the lead assessor is independent; otherwise two.
- 06Notify through MESOS
A plan to the deadline
ESOS Phase 4: a quarter-by-quarter plan
This is an indicative plan, not a regulatory timetable: only the dates in bold are set by law.
It assumes calendar year 2026 as the reference period — the earliest 12 months that include the qualification date.
Confirm the group and appoint
Map the UK group and the responsible undertaking; run the qualification test; choose audit or ISO 50001; approach lead assessors on the approved registers while diaries are open; start collecting 2026 energy data.
Qualification date
Phase 4 scope is fixed. Confirm, in writing, whether the group qualifies.
Close the reference period
Finalise 12 months of verifiable energy data; calculate total consumption per organisational purpose; decide whether to identify significant consumption.
Audit
Site and remote audits over the areas in scope; identify cost-effective savings; calculate savings achieved in kWh; review the Phase 3 action plan.
Lead assessor review
Review and sign-off of the assessment; assemble the evidence pack.
Confirm
Responsible officer or officers confirm compliance; the lead assessor’s seven-day notification to their approval body follows completion.
Notify
Submit the notification of compliance through MESOS.
Action plan
Notify the Phase 4 action plan; progress updates follow in 2029, 2030 and 2031.
Filing bunches at deadlines: in Phase 3, most first progress updates were filed in the final month before they fell due.
Lead assessor capacity is tightest in the final quarter, so check registers early — CIBSE’s ESOS lead assessor register is one of the seven.
How to choose and check a provider is set out on the ESOS consultants page, and the carbon legislation readiness check maps which other regimes apply to you.
The same energy data feeds annual SECR compliance, so plan the two together.
Carbon Legal is an independent guide and signs nothing off; it can introduce you to independent specialists — book a free 15-minute call or get in touch.
Action plan
The ESOS action plan deadline
The ESOS action plan is a statutory filing under regulation 34A: the energy-saving measures the organisation intends to implement, with estimated savings.
For Phase 4 it is due by 5 December 2028, the end of the first year of the following compliance period.
Three progress updates then report what has been implemented: by 5 December 2029, 5 December 2030 and 5 December 2031.
The third update is new, added by SI 2026/701 regulation 28.
Part 8 attaches no penalty to a missing action plan or progress update, but the Scheme Administrator publishes the failure, and a regulator can serve an enforcement notice whose breach is penalisable.
DESNZ has said it intends to consult on SECR and ESOS later in 2026, in the government’s Modernising corporate reporting consultation; none of these dates is affected unless and until the Regulations are amended.
The statutory ESOS action plan is a document you notify by 5 December 2028.
A project plan to reach the 5 December 2027 deadline is something else, and nobody files it.
Frequently asked
ESOS Phase 4 deadline — frequently asked
When is the ESOS Phase 4 deadline?
The ESOS Phase 4 deadline — the compliance date — is 5 December 2027. By then a qualifying organisation must have completed its ESOS assessment and notified compliance through MESOS, the Environment Agency’s notification system. The date is set by regulation 4 of the ESOS Regulations 2014.
Has the ESOS Phase 4 deadline changed?
No. 5 December 2027 follows from regulation 4 of the ESOS Regulations 2014, and the Phase 4 amending instrument, SI 2026/701, does not amend regulation 4. A sentence in the Environment Agency’s Phase 4 guidance saying the deadline was revised by the 2026 amendment is not borne out by the instrument. Phase 3’s compliance date was extended to 5 June 2024; that was Phase 3, not Phase 4.
What is the ESOS Phase 4 qualification date?
The qualification date is 31 December 2026. An undertaking that on that day employs at least 250 people, or has an annual turnover in excess of £44 million and an annual balance sheet total in excess of £38 million, qualifies for Phase 4, and so does the rest of its UK group.
When is ESOS Phase 4 due?
Phase 4 is due on 5 December 2027, the last day of the compliance period that began on 6 December 2023. The action plan is due a year later, by 5 December 2028.
When is the ESOS action plan deadline for Phase 4?
The Phase 4 action plan must be notified by 5 December 2028 — within the first year of the next compliance period, under regulation 34A. Progress updates follow by 5 December 2029, 5 December 2030 and 5 December 2031. Part 8 attaches no penalty to missing them, but the failure is published.
What reference period should the ESOS audit data cover?
A 12-month period that includes the qualification date, 31 December 2026, and ends on or before 5 December 2027. GOV.UK adds that the data must begin no earlier than 6 December 2022 and no earlier than 24 months before the audit starts. Calendar year 2026 is the earliest period that satisfies the qualification-date condition.
What are the ESOS Phase 4 requirements?
Measure total energy consumption across four organisational purposes; audit the areas of significant consumption (at least 95% if identified) or cover them with ISO 50001; have an approved lead assessor carry out or review the assessment unless exempt; report savings achieved and review the previous action plan; have one or two responsible officers confirm; notify by 5 December 2027; then submit an action plan and three progress updates.
What is the penalty for missing the ESOS Phase 4 deadline?
Failing to notify is an offence under regulation 43, with a penalty of up to £5,000 plus £500 for each working day the failure continues, capped at 80 working days, and publication. Failing to undertake the ESOS assessment itself carries £50,000, or a lesser amount the regulator determines, plus the same daily penalty.
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.ukEnergy Savings Opportunity Scheme Regulations 2014 (SI 2014/1643)
The principal instrument.
- legislation.gov.ukSI 2014/1643, regulation 4 — compliance periods and dates
4(2) the period; 4(3)(b) the qualification date; 4(4)(b) the compliance date.
- legislation.gov.ukSI 2014/1643, regulation 22 — the reference period
22(5): the 12-month period ends on or before the compliance date.
- legislation.gov.ukSI 2014/1643, Part 6A — action plans and progress updates
Regulation 34A(7)(b) and (10); regulation 34B(1)(a)–(c).
- legislation.gov.ukSI 2014/1643, Part 8 — civil penalties
Regulations 43 to 47.
- legislation.gov.ukEnergy Savings Opportunity Scheme (Amendment) Regulations 2026 (SI 2026/701)
In force 22 July 2026; does not amend regulation 4.
- legislation.gov.ukSI 2026/701, regulation 28 — the third progress update
Due by 5 December 2031.
- legislation.gov.ukSI 2026/701, regulation 8 — the lead assessor’s seven-day notification
New regulation 21(2A).
- Environment AgencyHow to comply with the Energy Savings Opportunity Scheme (ESOS) phase 4
Published 30 July 2026; §3.1 phase table. Internally inconsistent on the number of progress updates — the Regulations say three.
- GOV.UKEnergy savings opportunity scheme (ESOS): find out if you qualify and how to comply
Rewritten 2 September 2026: the audit data window and the ISO 50001 certificate window.
- ISOISO 50001 — Energy management
The standard behind the alternative route; the Regulations recognise the 2011 and 2018 editions.
- CIBSE CertificationESOS Lead Assessors register
One of the seven approved registers.
- GOV.UKModernising corporate reporting — consultation (7 September 2026)
¶150: DESNZ intends to consult on SECR and ESOS later in 2026.