ESOS phases — every date
2014 to 2031, sourced
Five compliance periods, one rolling four-year cycle, and one deadline that splits three ways. Every date below comes from regulation 4 — not from a table someone copied.
All five ESOS phases, with every date
Two dates matter per phase. The qualification date is the single day your size is measured. The compliance date is when the Environment Agency must have heard from you.
| Phase | Compliance period | Qualification date | Compliance date |
|---|---|---|---|
| 1 | 17 Jul 2014 – 5 Dec 2015 | 31 Dec 2014 | 5 Dec 2015 |
| 2 | 6 Dec 2015 – 5 Dec 2019 | 31 Dec 2018 | 5 Dec 2019 |
| 3 | 6 Dec 2019 – 5 Dec 2023 | 31 Dec 2022 | 5 Jun 2024 — and two other dates |
| 4 | 6 Dec 2023 – 5 Dec 2027 | 31 Dec 2026 | 5 Dec 2027 |
| 5 | 6 Dec 2027 – 5 Dec 2031 | 31 Dec 2030 | 5 Dec 2031 |
Phase 1’s period begins on 17 July 2014, when the Regulations came into force — not 6 December 2011, which is a different date doing a different job. Phase 2 onward are produced by applying regulation 4 recursively; the Environment Agency publishes the same table in its Phase 4 guidance of 30 July 2026.
Photo: Unsplash / Ricardo Gomez AngelThe word “phase” is not in the ESOS Regulations
Not once, in a 197KB instrument. The law knows only an initial compliance period and a subsequent compliance period.
“Phase 1”, “Phase 4”, “Phase 5” are Environment Agency vocabulary and industry shorthand. Useful shorthand — this page uses it too — but it has no statutory existence, which is why you will not find a regulation that “sets the Phase 5 dates”. None does.
What regulation 4 does instead is define a cycle that runs itself:
4.—(1) The “initial compliance period” means the period which begins on the coming into force of these Regulations and ends on 5th December 2015.
(2) A “subsequent compliance period” means a period which— (a) begins on the 6th December immediately following the end of the preceding compliance period, and (b) ends on the 5th December four years later.
(3) The “qualification date” means— (a) in relation to the initial compliance period, 31st December 2014, (b) in relation to a subsequent compliance period, the 31st December immediately preceding the compliance date for that compliance period.
Three sentences, and they generate every date in the table above. Only two dates are hard-coded — 5 December 2015 and 31 December 2014. Everything after that is recursion: start on 6 December, run four years to 5 December, qualify on the 31 December before the end.
This has a consequence worth holding on to. The dates are about as stable as anything in UK compliance gets, because moving them takes a new instrument. The content of each phase has no such protection — it can change mid-period, and did: SI 2026/701 rewrote parts of Phase 4 on 22 July 2026, four years into it.
Twelve years of ESOS, and where you are standing in it
Past periods are closed and cannot be reopened. The one you are in now is Phase 4.
Why Phase 3 has three compliance dates, and every guide picks a different one
This single regulation is the reason searching “the ESOS deadline” returns contradictory answers.
Phase 3 should have ended on 5 December 2023. Guidance and legislation were both late, so an extension was granted — but not a clean one. SI 2023/1182 substituted regulation 4(4), and what it produced is a compliance date that depends on what you are doing:
Notification of compliance, the ESOS report, publication, and the related regulations 10, 22(3), 26(4), 27A, 29 and Schedule 2 paragraphs 7 and 7A. This is the operative deadline for almost every participant.
Every other purpose in the Regulations kept the original date. It did not disappear; it just stopped being the date most people needed.
For regulations 33 and 34 — the ISO 50001 route and, at the time, Display Energy Certificates — the participant could choose which date applied.
So a page that says “the Phase 3 deadline was 5 December 2023” is not simply wrong; it is right about a shrinking set of purposes and wrong about the ones that mattered. A page that says “5 June 2024” is right about the operative purposes and silent about the rest. Both are published widely, which is why the question feels unanswerable if you only read summaries.
Phase 4 and Phase 5 revert to the clean pattern: a single compliance date, 5 December, four years after the period opened. Phase 3 is the exception, not the rule — and there is no reason to expect it to repeat.
What changed between the phases
The dates are a fixed cycle. The obligations inside them have moved almost every time.
Thresholds went to sterling
SI 2018/1342 replaced the euro figures with £44m turnover and £38m balance sheet, binding from IP completion day — 31 December 2020. Note: the unrevised /schedule/1/made on legislation.gov.uk still shows the euro figures; the sterling ones appear only on the revised text.
Late, and then extended
SI 2023/1182 arrived 29 November 2023, days before the original deadline, and split the compliance date three ways.
Action plans and progress updates
The 2023 reforms introduced the ESOS action plan and annual progress updates — the point at which ESOS stopped being an audit you file and became a commitment you report against.
DECs and Green Deal removed
SI 2026/701, in force 22 July 2026, omitted regulation 34 entirely. If your Phase 3 compliance route was a Display Energy Certificate, you need a different one.
Savings actually achieved
New regulation 27D requires an estimate in kWh of the savings you actually delivered, broken down by purpose, measure and category — the hardest of the 2026 changes to retrofit.
Net zero, deferred
Consulted on in 2021, promised for Phase 4 in 2022, postponed to Phase 5 in February 2025. Nothing has been published since. The Phase 5 position →
Phase dates published elsewhere that the legislation does not support
Each checked against the instrument on legislation.gov.uk.
| Published claim | What regulation 4 says |
|---|---|
| Phase 1 ran from 6 December 2011 | The initial compliance period begins when the Regulations come into force — 17 July 2014. 6 December 2011 is the earliest date from which a pre-existing audit could be counted toward Phase 1, which is a different thing. |
| Phase 5 qualification date is 31 December 2027 | 31 December 2030. Regulation 4(3)(b) makes the qualification date the 31 December immediately preceding the compliance date. With a compliance date of 5 December 2031, no other answer is available — and 31 December 2027 falls 25 days after Phase 5 opened. |
| The Phase 3 deadline was 5 December 2023 | True for residual purposes only. For notification, the ESOS report and publication it is 5 June 2024. The three-way split → |
| The 2023 amendment is SI 2023/1364 | SI 2023/1182. SI 2023/1364 is not an ESOS instrument. The full instrument stack → |
Which phase applies to you right now
In August 2026 the answer is Phase 4 for everyone. What differs is what you still owe from earlier periods.
That single day decides whether Phase 4 applies. Your size before or after it is irrelevant to this period. The qualification test →
Assessment complete, lead assessor review done, notification made. The Phase 4 guide →
The action plan cycle from Phase 3 runs past the end of that period. Closing Phase 3 was not the end of Phase 3 reporting.
Its qualification date is more than four years away and its content is unwritten. What is worth doing now is the data work Phase 4 already demands.
ESOS phases FAQs
Five have begun. Phase 1 ran to 5 December 2015, Phase 2 to 5 December 2019, Phase 3 to 5 June 2024, Phase 4 runs to 5 December 2027 and Phase 5 to 5 December 2031. There is no final phase: regulation 4 defines a rolling four-year cycle that continues indefinitely unless an instrument stops it, so Phase 6 would run to 5 December 2035 on the same arithmetic.
Phase 1: qualified 31 December 2014, complied 5 December 2015. Phase 2: 31 December 2018 and 5 December 2019. Phase 3: 31 December 2022 and 5 June 2024. Phase 4: 31 December 2026 and 5 December 2027. Phase 5: 31 December 2030 and 5 December 2031. Every qualification date is the 31 December immediately preceding that phase's compliance date, under regulation 4(3)(b).
Phase 4, which runs from 6 December 2023 to 5 December 2027. Its qualification date has already passed — 31 December 2026 — so whether it applies to you is already settled by your size on that day. Phase 5 opens on 6 December 2027.
Because regulation 4(4), as substituted by SI 2023/1182, gives Phase 3 three compliance dates depending on purpose: 5 June 2024 for notification, the ESOS report and publication; 5 December 2023 for all other purposes; and either, at the participant's election, for regulations 33 and 34. A source quoting one date without the others is incomplete rather than simply wrong, which is why the disagreement persists.
Its dates are, in the sense that regulation 4 generates them automatically and no further legislation is needed. Its content is not: as at 14 August 2026 there is no Phase 5 instrument, consultation or draft guidance. The Environment Agency does publish the Phase 5 compliance period in its Phase 4 guidance table, so the dates are stated by the regulator as well as derivable from the law.
No. Regulation 4(1) begins the initial compliance period when the Regulations came into force, which was 17 July 2014. The 2011 date that circulates comes from a transitional allowance: energy audits carried out from 6 December 2011 onward could be counted toward Phase 1 compliance. That is a rule about what evidence was admissible, not about when the period started.
Primary sources
Every date on this page traces to one of these, each opened and read on 14 August 2026.