ESOS Phase 4 · read from SI 2014/1643 and SI 2026/701

ESOS Phase 4: the thresholds and requirements, as the Regulations write them

ESOS Phase 4 turns on one date and one test: whether an undertaking is large on 31 December 2026, under Schedule 1 to the ESOS Regulations 2014.

The qualification criteria are at least 250 employees, or turnover in excess of £44 million and a balance sheet in excess of £38 million.

Everything a qualifying group owes by 5 December 2027 comes from the 2026 amending Regulations read with the 2014 text, and this page cites the provision for each.

Check your figures What Phase 4 requires

Qualification datestatus judged31 Dec 2026
Compliance datenotify by5 Dec 2027
Action plandue5 Dec 2028
Progress updatesdue2029, 2030, 2031
Employee limbat least250 persons
Money limbsboth exceeded£44m and £38m

Two tests decide Phase 4

At least 250 people, or over £44m and £38m, on one date: 31 December 2026.

Everything below reads the provision behind each number.

The scheme

What ESOS is, in the Regulations’ own terms

The Energy Savings Opportunity Scheme is a four-yearly energy assessment that large UK undertakings and their corporate groups must carry out and report.

It is established by the Energy Savings Opportunity Scheme Regulations 2014, in force since 17 July 2014.

It does not require anyone to cut energy use.

It requires a participant to measure what it uses, have the significant part examined, identify cost-effective savings, have a responsible officer confirm the result, and notify the regulator that it has done so.

The Environment Agency is the scheme administrator for the whole UK, and the regulator for undertakings whose registered office is in England.

Regulation 6 names the other compliance bodies: Natural Resources Wales, the Chief Inspector in Northern Ireland (the Northern Ireland Environment Agency), SEPA in Scotland, and the Secretary of State for offshore undertakings.

Phases run from 6 December to 5 December four years later, and regulation 4 generates every date from that formula.

The same scheme is summarised on the ESOS hub, and the change from the last cycle on ESOS Phase 3 vs Phase 4.

Environment Agency Phase 4 guidance §3.1; Phase 4 derivable from SI 2014/1643 reg 4.
Phase	Qualification date	Compliance date
1	31 Dec 2014	5 Dec 2015
2	31 Dec 2018	5 Dec 2019
3	31 Dec 2022	5 Jun 2024 (extended)
4	31 Dec 2026	5 Dec 2027
5	31 Dec 2030	5 Dec 2031

The instruments

ESOS regulations: one scheme, three instruments

ESOS law is the 2014 Regulations as amended twice.

The 2026 amendments are only partly consolidated on legislation.gov.uk, so a Phase 4 citation names the 2014 provision and the regulation of SI 2026/701 that changed it.

Dates from each instrument's commencement provision and legislation.gov.uk's amendment notes.
Instrument	In force	What it did	Made under
SI 2014/1643	17 July 2014	Created ESOS: qualification, the audit, notification, penalties	European Communities Act 1972 s.2(2)
SI 2023/1182	29 November 2023	Phase 3 changes: action plans and progress updates (Part 6A), the 95% line, site visits, the ESOS report, intensity ratios	Energy Act 2023
SI 2026/701	22 July 2026	Phase 4 changes: DECs and Green Deal assessments removed, the ISO 50001 route widened, savings achieved, the action plan review, a third progress update	Energy Act 2023 ss.254–260, 263

The ESOS legislation began as the UK’s transposition of Article 8(4) to (6) of the Energy Efficiency Directive 2012/27/EU, which the Regulations still cross-refer to for the meaning of “energy”.

That Directive was repealed in October 2025 by the 2023 recast, and it is cited here for the scheme’s origin, not as current law.

The live power to make ESOS regulations is the Energy Act 2023, under which the 2026 amendments were made on 23 June 2026.

The financial limbs were written in euro until the EU Exit amendments (SI 2018/1342) substituted sterling for any qualification date on or after 31 December 2020.

The Environment Agency’s Phase 4 guidance of 30 July 2026 restates the law; where the two differ, this page follows the instrument and says so.

The earlier guidance collection still serves Phase 3 material and is not a source for any Phase 4 figure, and the GOV.UK ESOS overview was rewritten for Phase 4 on 2 September 2026.

Whether the scheme binds you, and under which power, is taken further on is ESOS mandatory.

Who and how often

Who needs to do ESOS, and how often

ESOS applies to large undertakings, to the small and medium undertakings in their corporate groups, and to nobody else.

The size test is in Schedule 1 and the group rule in regulation 15; the tool beside this text walks the questions in the order the Regulations ask them.

The scheme is every four years because each compliance period runs from 6 December to 5 December four years later, and regulation 4 repeats the formula.

Qualification is re-tested on the 31 December before each compliance date, so a participant in Phase 3 is not automatically in Phase 4.

Phase 3qualified31 Dec 2022
Phase 4qualifies31 Dec 2026
Phase 5qualifies31 Dec 2030
Phase 6qualifies31 Dec 2034

The dates in that line are arithmetic on regulation 4, which is why Phase 6 is shown, and only Phases 4 and 5 are set out in the Environment Agency’s guidance.

Who needs to do ESOS?

Are you a public body?

reg 16(1)(a)

The date

Qualification: who is in on 31 December 2026

Regulation 15 makes an undertaking a relevant undertaking if, on the qualification date, it is a large undertaking, or a small or medium undertaking that is a group undertaking of a large one.

Regulation 4(3)(b) sets the qualification date as the 31 December immediately before the compliance date, which for Phase 4 is 31 December 2026.

The test is applied to each undertaking in a group, not to consolidated group figures.

A group that reports on a consolidated basis still has to ask whether any single undertaking inside it is large on its own figures.

Size is not a one-year snapshot: Schedule 1 paragraph 11 keeps an undertaking at its size until it has been the other size for two consecutive accounting periods.

So a group that shrank below the limbs in its latest accounts is still large if it had not stayed small for two periods, and a growing company that crossed the line once is still small.

The Environment Agency’s guidance, section 1.6, works the rule through a five-year table and notes there is no limit on how far back the look can go.

Once the date has passed, status is fixed: a qualifying undertaking still complies by 5 December 2027 whatever happens to its size or structure in the eleven months between.

31 Dec 2026

Qualification date — the status on this day decides Phase 4

SI 2014/1643 reg 4(3)(b)

2 periods

Consecutive accounting periods before a size status changes

Sch 1 ¶11

250 personsThe employee limb: at least 250 persons qualifies, 249 does notAt least 250

Source line: SI 2014/1643 Sch 1 ¶1(a), ¶1A, ¶11 — Schedule 1; the amounts were converted to sterling by SI 2018/1342.

The test

The ESOS thresholds, limb by limb

Schedule 1 paragraph 1(a) defines a large undertaking as one which either employs at least 250 persons, or has an annual turnover in excess of amount A and an annual balance sheet total in excess of amount B.

Paragraph 1A fixes amount A at £44 million and amount B at £38 million.

The drafting is deliberately uneven: exactly 250 persons qualifies, but exactly £44 million of turnover does not.

The two money limbs are one test with two parts, joined by “and”; exceeding one of them is not enough.

Who counts as employed

Paragraph 9 counts employees, owner managers and partners, and regulation 2 takes “employee” from section 230(1) of the Employment Rights Act 1996.

Paragraph 10 uses a monthly average over the accounting period that supplies the financial figures, not a count on 31 December.

A seasonal business therefore averages its peaks and troughs, month by month, like everyone else.

The Environment Agency’s guidance adds that agency workers usually do not count, and that a UK undertaking includes people it employs directly overseas.

Which accounts

Paragraph 5 takes turnover and balance sheet total from the accounts for the financial year ending on, or in the 12 months immediately before, the qualification date.

For a December year-end, that is the year ending 31 December 2026 itself.

Turnover has its Companies Act 2006 section 474(1) meaning (paragraph 4), and the guidance reads the balance sheet total as gross assets, before liabilities.

An undertaking that prepares no individual accounts estimates both figures for a 12-month period including the qualification date (paragraph 7).

The same test applied to scope under other regimes is set out on UK SRS thresholds, which work on listing category, not size.

Phase 4 check · one undertaking at a time

Figures for the accounting period ending on, or in the 12 months before, 31 December 2026.

Average persons employedpeopleTurnover£mBalance sheet total£m

The accounting period before this one

Another undertaking in my corporate group is a large undertakingWe are a public bodyWe will be in insolvency proceedings between 31 Dec 2026 and 5 Dec 2027

Not in scopeOut on these figuresUnder 250 persons, and not over both money limbs. Check the group before relying on this.SI 2014/1643 Sch 1 ¶¶1, 11; reg 15

Your 12-month reference period

First day of the period

Valid: 1 January 2026 to 31 December 2026.

It ends on or before 5 December 2027 and includes 31 December 2026.

SI 2014/1643 reg 22(5); EA Phase 4 guidance §4.4

Indicative, not advice.

It tests one undertaking; groups, overseas parents and disaggregation are set out in the section beside it.

Nothing you enter leaves your browser.

Groups

One large undertaking brings in the UK group

A small or medium undertaking is brought in by regulation 15(1)(b) whenever it is a group undertaking of a large undertaking.

“Group undertaking” and “parent undertaking” take their meanings from sections 1161 and 1162 of the Companies Act 2006, so the group is the Companies Act group.

Regulation 17(2) makes the undertakings under a common highest parent one participant, which complies once for all of them.

By default the highest UK parent is the responsible undertaking, and another member can take the role only if every undertaking in the group agrees in writing.

Members may also disaggregate and comply separately by written agreement with the highest parent, but each resulting participant must still cover at least 95% of its own energy.

Overseas group members are not ignored: UK groups that share an overseas parent are one corporate group for qualification, which is how a small UK sub-group can be pulled in by a large sister.

What does stay out is overseas turnover and balance sheet held in overseas-registered subsidiaries, which the guidance excludes from a UK undertaking’s own figures.

One large undertakingin the group

Select a node

Tap or focus any regime to stop the orbit and read what it asks of the company at the centre.

Environment Agency Phase 4 guidance §§1.2.1, 2 and 2.3, read with SI 2014/1643 regs 15 and 17.
Group shape	Phase 4 result
UK parent under the limbs, one subsidiary with 400 employees	The whole highest UK parent group takes part
Two UK sub-groups under one overseas parent; one contains a large undertaking	Both UK sub-groups take part, separately by default
Overseas company with a UK establishment employing 250 in the UK	Qualifies in its own right
Overseas company with UK energy supplies but no qualifying UK establishment	Out, unless another UK part of its group qualifies
Franchisor and franchisees	Not grouped, unless one is the parent of the other

Deals and restructurings

Acquisitions, disposals and reorganisations

Status is judged on 31 December 2026 and fixed until 5 December 2027.

Energy is counted for assets held on 31 December 2026, and may be dropped for assets no longer held on 5 December 2027 (reg 22(2)–(3)).

Because paragraph 11 carries size across two periods, a restructuring timed just before 31 December 2026 may not change the answer at all.

Where a transaction straddles the qualification date, it is a legal question for the group’s advisers, and the analysis turns on the Companies Act group on that day.

Part of the group on the qualification date

An undertaking acquired before 31 December 2026 is in the buyer’s group on the date that decides status, and its size counts towards the group’s test.

SI 2014/1643 reg 4(3)(b), reg 15(1)

Sources: regulation 15, regulation 22 and EA guidance §2.8.

Exclusions

Who is out of scope, and who only looks it

Regulation 16 takes public bodies out, and since 24 February 2025 a public body is defined by reference to the Procurement Act 2023.

The Environment Agency’s guidance still describes the test through the Public Contracts Regulations, so where the two differ the regulation governs.

Central government departments report their own environmental performance under a separate framework, the Greening Government Commitments.

SI 2026/701 widened the insolvency exclusion: proceedings at any point from the qualification date to the compliance date now count, not only on the qualification date.

Charities, partnerships, LLPs, trusts and universities funded mainly from private sources can all be undertakings, and are in if they are large.

A qualifying undertaking with zero energy consumption is not out: regulation 33A spares it the assessment, but it still notifies, with two directors confirming it has no energy responsibility.

Private companies that are in ESOS may also wonder about UK SRS; that question is answered on private companies and UK SRS, and the short version is that no private-company threshold has been proposed.

Case	In Phase 4?	Provision
Public body	No	reg 16(1)(a)
In insolvency proceedings between 31 Dec 2026 and 5 Dec 2027	No	reg 16(1)(b)
Small or medium member whose only large group member is insolvent	No	reg 16(1)(c)
Qualifies but uses no energy	Yes — must still notify	reg 33A
Under the limbs, and no large group member	No	reg 15

The duties

ESOS Phase 4 requirements, provision by provision

Once a participant qualifies, the duties are the same whichever limb brought it in.

Each row is a duty in the Regulations, with the Phase 4 change where there is one.

SI 2014/1643 as amended by SI 2023/1182 and SI 2026/701.
Duty	What it asks	Provision
Total energy consumption	12 consecutive months, beginning no more than 12 months before 31 Dec 2026 and ending on or before 5 Dec 2027	reg 22
Significant energy consumption	Optionally identify areas making up not less than 95% of the total, by energy units or by spend	reg 25(1)–(2)
Energy intensity ratios	One for each organisational purpose used: transport, industrial process, buildings, other	reg 25C
Lead assessor	Appointed from an approved register, unless under 40,000 kWh, ISO 50001 covers the energy, or consumption is zero	reg 21
Energy audit	Site visits, verifiable data, savings opportunities with costs, benefits and payback	regs 26–27
ESOS report	Now including the energy savings achieved (reg 27D) and the review of the last action plan (reg 27E)	SI 2026/701 reg 17
Responsible officer	One if the lead assessor is independent of the participant, two otherwise	reg 30
Notification	Through the Notification System, after 31 Dec 2026 and by 5 Dec 2027	reg 29
Evidence pack	Records kept, now including the data behind every estimate	reg 28
Action plan and three progress updates	By 5 Dec 2028, then 2029, 2030, 2031	Part 6A

Three of those rows are new in Phase 4, and they are the part most summaries still miss.

The report and notification must state the energy savings actually achieved in the compliance period, in kWh, measure by measure, and only the combined figure is published.

They must also identify the measures in the last action plan that were not implemented, and why, and that review is not published.

And regulation 28 of SI 2026/701 adds a third progress update, so Phase 4 has three rather than two.

The lead assessor now carries a personal duty of its own: to notify its approval body within seven days of the assessment’s completion, naming two contacts at the participant.

The sequence as a working order is on ESOS compliance, the audit itself on ESOS energy audits, and the plan on the ESOS action plan.

Step 1
Find the participant
Test every undertaking, then take the highest UK parent group as one participant.
By default the highest UK parent is the responsible undertaking.
regs 15, 17
Step 2
Total energy consumption
Calculate it over a 12-month reference period that begins no more than 12 months before 31 December 2026 and ends by 5 December 2027, for assets held on the qualification date.
reg 22(2), (5)
12 months consecutive, reg 22(5)
Step 3
Significant energy consumption
Optionally identify areas making up not less than 95% of the total, by energy units or by spend.
Without that step the audit covers the total.
reg 25
95% not less than, reg 25(2)
Step 4
Energy intensity ratios
Calculate at least one for each organisational purpose, except where that purpose’s consumption is zero.
regs 25B–25C · regulation 25C
Step 5
Appoint a lead assessor
Appoint one from an approved register, unless consumption is under 40,000 kWh, ISO 50001 covers the energy, or consumption is zero.
reg 21
40,000 kWh below this, no lead assessor
Step 6
The energy audit
Site visits, verifiable data, and identified savings with costs, benefits and payback, over data that meets the audit window.
regs 26–27; EA guidance §8.3
Step 7 · new in Phase 4
The ESOS report
Produce it before the compliance date.
In Phase 4 it states the energy savings achieved, in kWh, and reviews the measures in the last action plan that were not implemented.
reg 27A; regs 27D, 27E
Step 8
Responsible officer sign-off
One responsible officer if the lead assessor is independent of the participant, two otherwise.
reg 30
Step 9 · by 5 December 2027
Notify
Through the Notification System after 31 December 2026 and by 5 December 2027.
Notification is free and the regulators cannot move the date.
reg 29; EA guidance §§12.1, 15.1
Step 10
Keep the evidence pack
At least two compliance periods after the one it relates to, so to at least 5 December 2035 for Phase 4.
reg 28(2)
2 further compliance periods
Step 11 · third update new
Action plan and progress updates
The plan by 5 December 2028, then updates by 5 December 2029, 2030 and 2031.
regs 34A, 34B; SI 2026/701 reg 28
3 progress updates after the plan

Sources: SI 2014/1643 as amended by SI 2026/701; Environment Agency Phase 4 guidance.

Routes

Two routes to compliance, and the ones that closed

A participant covers its significant energy consumption, or its total if it did not identify the significant part, by an energy audit, an ISO 50001 certificate, or a mix of the two.

Regulation 26 of SI 2026/701 omitted regulation 34 of the 2014 Regulations, and with it Display Energy Certificates and Green Deal assessments as routes.

Data gathered for a DEC can still inform an intensity ratio; it cannot stand in for the audit.

An ISO 50001 energy management system that covers all of the total or significant consumption now deems compliance with the lead assessor, audit and report duties; before 22 July 2026 it had to cover total consumption, and the report was not deemed.

It never deems the notification, and it never replaces the duty to carry out an ESOS assessment as such.

The route in detail is on ISO 50001 and ESOS.

Which route covers my energy?

Does an ISO 50001 certificate cover all of your total, or your significant, energy consumption?

reg 33

Sources: SI 2026/701 reg 26, reg 20; UKAS; lead assessor registers such as CIBSE Certification; voluntary PAS 51215-1:2025.

Route	Phase 4 status
ESOS energy audit	Open
ISO 50001 over total or significant consumption	Open — deems lead assessor, audit and report
Display Energy Certificates	Closed — SI 2026/701 reg 26
Green Deal assessments	Closed — SI 2026/701 reg 26

Phase 3 to Phase 4

What changed in ESOS Phase 4, on one toggle

SI 2026/701 changed the routes, the report, the updates and the lead assessor, and left the thresholds and the dates alone.

Switch between the two cycles; the text beside each side says what moved.

Phase 3

Four routes, an ISO 50001 route that had to cover total consumption, a report with no savings-achieved figure and two progress updates.

Phase 4

Two routes, ISO 50001 over total or significant consumption, a report with savings achieved and an action plan review, three progress updates and a seven-day lead assessor notification.

Simplified; sources: SI 2023/1182, SI 2026/701 regs 17, 24, 26, 28; ESOS Phase 3 vs Phase 4 goes row by row.

The dates

ESOS Phase 4 deadlines, from qualification to the last update

Every Phase 4 date is arithmetic on regulation 4 and Part 6A, which is why the page can state them without leaning on the guidance table.

The action plan and progress updates fall in statutory windows set by regulations 34A(7) and 34B(1), and 5 December is the last day of each window.

The Environment Agency’s guidance contradicts itself on the number of progress updates: its stages list gives two, and its section 14 gives three.

The instrument says three, the last added by regulation 34B(1)(c) for compliance periods ending on or after 5 December 2027.

SI 2026/701 did not amend regulation 4, so no compliance date changed in 2026, whatever the guidance’s penalty section implies.

6 Dec 2023
Phase 4 compliance period begins
reg 4
22 Jul 2026
SI 2026/701 in force
legislation.gov.uk
30 Jul 2026
EA Phase 4 guidance published
Environment Agency
5 Dec 2026
Phase 3 second progress update due
For Phase 3 participants.
Part 6A
31 Dec 2026
Phase 4 qualification date
reg 4
5 Dec 2027
Compliance date — notification due
reg 4, reg 29
5 Dec 2028
Action plan due
Covers 6 Dec 2027 to 5 Dec 2031.
reg 34A(7)
5 Dec 2029
Initial progress update
reg 34B
5 Dec 2030
Further progress update
reg 34B
5 Dec 2031
Final progress update — new in Phase 4
reg 34B(1)(c)

Phase 3

ESOS Phase 3 qualification date and deadlines

The Phase 3 qualification date was 31 December 2022, the 31 December immediately before the formula compliance date of 5 December 2023 (regulation 4).

The Phase 3 compliance period ran from 6 December 2019, and the test was the same Schedule 1 test, at the then-current sterling amounts.

The Environment Agency’s guidance says the Phase 3 compliance date was extended for six months to 5 June 2024, while the fourth compliance period began on 6 December 2023 regardless (Phase 4 guidance §3).

Phase 3 action plans were due by 5 December 2024 under regulation 34A(7)(a), and the Agency accepted them until 5 March 2025.

The remaining Phase 3 date is the second progress update on 5 December 2026, set out in the Agency’s Phase 3 guidance.

Phase 3 status does not carry into Phase 4: qualification is judged afresh on 31 December 2026, though the two-period rule in paragraph 11 can keep a participant at its old size.

6 Dec 2019
Compliance period begins
reg 4
31 Dec 2022
Qualification date
Size and group status judged.
reg 4
5 Dec 2023
Formula compliance date
EA guidance
5 Jun 2024
Extended compliance date
The guidance: extended for six months.
EA guidance
5 Dec 2024
Action plan deadline
Accepted until 5 March 2025.
reg 34A(7)(a)
5 Dec 2025
First progress update
reg 34B
5 Dec 2026
Second progress update
EA Phase 3 guidance

Has it moved?

Has the ESOS deadline been extended? The Phase 4 date, checked

No Phase 4 date has moved: the compliance date is 5 December 2027, the qualification date 31 December 2026 and the action plan date 5 December 2028.

Regulation 4 generates every compliance date from a formula, and SI 2026/701 did not amend it, so searches for a new, updated or extended ESOS deadline have nothing to find.

The Environment Agency’s guidance says the regulators cannot amend the compliance deadline (§15.1).

The one extension in recent practice was Phase 3’s, by six months to 5 June 2024, and the action plan window stayed 5 December 2024 although the Agency accepted plans until 5 March 2025.

An accepted late filing is the Agency’s forbearance, not a new statutory date.

The windows each date sits in are drawn on the windows diagram below.

Counted as at 1 October 2026

91days to the Phase 4 qualification date31 December 2026 · reg 4

430days to the Phase 4 compliance date5 December 2027 · reg 4, reg 29

796days to the Phase 4 action plan date5 December 2028 · reg 34A(7)

Counted in your browser from today’s date; nothing is stored or sent.

The reference period

The ESOS reporting period: what the regulation says, and what the guidance adds

Searches for the ESOS reporting period are asking which 12 months of energy use to measure.

Two documents answer, and they are not the same.

31 Dec 2025
Earliest start under reg 22(5)(a)
No more than 12 months before the qualification date.
reg 22(5)
1 Jan 2026
Earliest start that includes 31 Dec 2026
A period beginning 31 December 2025 ends on 30 December 2026.
our arithmetic, on EA §4.4
6 Dec 2026
Latest start
A 12-month period beginning here ends on 5 December 2027.
reg 22(5)(b)
31 Dec 2026
Qualification date
reg 4
5 Dec 2027
Compliance date
The period ends on or before this day.
reg 4

Regulation 22(5) says the reference period is a period of 12 consecutive months which begins no more than 12 months before the qualification date and ends on or before the compliance date (regulation 22).

The Environment Agency’s guidance, section 4.4, says the period must include the qualification date and end before the compliance date (Phase 4 guidance).

That sentence is the Agency’s, and it is stricter than the regulation in two ways: it requires the qualification date to fall inside the period, and it says “before” where the regulation says “on or before”.

The two bite at the edge: the earliest start the regulation allows, 31 December 2025, gives a period ending on 30 December 2026, a day short of the qualification date.

The reference-period checker in the qualification check shows both readings for any start date.

The windows

The windows inside those dates

Phase 4 has seven moving windows, and three of them are easy to mis-set. Each bar below prints its own dates, drawn from the provision named in the source line.

Audit data floor to compliance date6 Dec 2022 – 5 Dec 2027

Compliance period6 Dec 2023 – 5 Dec 2027

Reference period, widestbegins 31 Dec 2025 at the earliest; ends by 5 Dec 2027

Notification windowafter 31 Dec 2026, by 5 Dec 2027

Action plan window6 Dec 2027 – 5 Dec 2028

Progress updatesdue 5 Dec 2029, 2030, 2031

Evidence pack kept untilat least 5 Dec 2035

Sources: regulation 4, regulation 22(5), EA guidance §§8.3, 11, 12.4, Part 6A, regulation 28(2).

The reference period for total energy consumption is 12 consecutive months that begin no more than 12 months before 31 December 2026 and end on or before 5 December 2027, under regulation 22(5).

The audit data window is set by regulation 26(4)(b) and restated in the Environment Agency’s guidance: data begins no earlier than 6 December 2022 and no earlier than 24 months before the audit starts.

The Agency says it will publish Phase 4 data on 10 June 2028, while regulation 10(2) read literally gives 4 June 2028, and both dates are recorded here because nothing read says which convention applies.

The evidence pack is kept for at least two further compliance periods, which puts the end of Phase 4’s retention at 5 December 2035 under regulation 28(2).

Energy intensity ratios under regulation 25C need at least one for each organisational purpose, but none for a purpose whose consumption is zero.

The audit

The Phase 4 ESOS audit: which data it can use

An ESOS energy audit rests on verifiable data covering 12 months, and regulation 26(3A) asks for site visits representative of how energy is used (regulations 26–27).

Regulation 26(4)(b) bounds that data period: it begins no more than 12 months before the start of the compliance period and no more than 24 months before the audit commences, and it ends on or before the compliance date.

For Phase 4 the first limb puts the floor at 6 December 2022, and the second moves the floor forward for any audit that starts after 6 December 2024.

The Environment Agency’s guidance, section 8.3, states the same two floors (Phase 4 guidance).

An audit starting on 1 June 2026, for instance, cannot use data from before 1 June 2024.

The audit itself is taken further on ESOS energy audits.

When does the audit start?

First day of the energy audit

The 12-month data period can begin no earlier than 1 June 2024, set by the 24-month rule.

It can begin no later than 6 December 2026, so that it ends on or before 5 December 2027.

SI 2014/1643 reg 26(4)(b); EA Phase 4 guidance §8.3

The bounds on the data period, not advice on which period to choose.

After notification

The ESOS action plan deadline: Phase 3 and Phase 4

The action plan has a statutory window of its own, set by regulation 34A(7), and the progress updates have theirs under regulation 34B.

Searches for the Phase 4 action plan are asking when, and the answer is a year after notification.

Part 6A as consolidated to 22 July 2026; Phase 4 dates by arithmetic on regulation 4, with the plan date as stated in the Environment Agency’s guidance.
Filing	Phase 3	Phase 4	Provision
Notification of compliance	5 Dec 2023, extended to 5 Jun 2024	5 Dec 2027	reg 4; reg 29
Action plan	5 Dec 2024 (Agency accepted to 5 Mar 2025)	5 Dec 2028, covering 6 Dec 2027 – 5 Dec 2031	reg 34A(7)
First progress update	5 Dec 2025	5 Dec 2029	reg 34B
Second progress update	5 Dec 2026	5 Dec 2030	reg 34B
Third progress update	None	5 Dec 2031	reg 34B(1)(c)

Regulation 34A(3) requires the plan to list each measure the participant proposes to implement before the end of the relevant compliance period, or to state that there is none (regulation 34A).

The plan is entered through the Notification System, and Part 8 names neither the plan nor an update.

The Phase 4 plan is explained on the ESOS action plan page.

How many take part

What Phase 3 shows about participation

The government’s own post-implementation review of July 2025 counted 9,871 groups the Environment Agency believed qualified for Phase 3.

Of those, 8,581 notified, and 5,403 submitted an action plan.

The review recommended keeping the scheme without major changes.

The notification data itself is published by the Environment Agency as a dataset, and the wider research is collected in DESNZ’s energy audits and reporting research.

Believed to qualify (Environment Agency estimate)

9,871

Submitted a notification of compliance

8,581

87% of the estimate

Submitted an action plan

5,403

76% of notifiers

Phase 3 compliance, groups — source: DESNZ second post-implementation review, ¶19, 18 July 2025.

Penalties

The penalty table, and the gap in it

Part 8 sets five civil penalties, each a fixed maximum the regulator may reduce, three with a daily element counted in working days.

The daily cap is 80 working days, which is how the headline figures of £45,000 for failure to notify and £90,000 for failure to undertake the assessment are reached.

Every penalty can be published, naming the undertaking, the requirement breached and the amount, for at least a year.

Regulations 34A and 34B, the action plan and the progress updates, are named nowhere in Part 8, so no penalty attaches to missing them.

That is a gap in the statute, and the Environment Agency confirms it will not take enforcement action for non-submission, though it publishes the failure.

The residual route is regulation 46: a regulator that served an enforcement notice requiring a plan could penalise the failure to comply with that notice.

How amounts are set under the Agency’s enforcement and sanctions policy is on ESOS penalties.

Reg 43: failure to notify

£45,000

£5,000 plus £500 a working day, up to 80

Reg 44: failure to keep records

£5,000

plus the regulator’s audit costs

Reg 45: failure to undertake the assessment

£90,000

£50,000 plus £500 a working day, up to 80

Reg 46: failure to comply with a notice

£45,000

£5,000 plus £500 a working day, up to 80

Reg 47: false or misleading statement

£50,000

no daily amount

Highest amounts, each reducible — source: SI 2014/1643 Part 8, regs 43–47; every one also carries the publication penalty.

Misreadings

Common qualification mistakes, each against its provision

1 / 9

Sources: Schedule 1, regulation 15, SI 2018/1342.

Each of these has appeared in published guidance, and most can be settled by opening Schedule 1, which is a single page.

Law-firm commentary such as Linklaters’ note on preparing for Phase 4 is useful reading, and it is commentary rather than a source for any figure on this page.

Other regimes

ESOS beside SECR and UK SRS

ESOS is not a reporting standard, and it is not SECR: SECR is an annual disclosure in the directors’ report (see the government’s SECR guidance), with its own two-of-three exemption test at £36 million, £18 million and 250 employees.

An undertaking can be in one and not the other, which is why the two tests are set side by side on ESOS vs SECR and SECR thresholds.

UK SRS S1 and S2 are voluntary standards, reported against on a comply-or-explain basis by listed companies in scope of the FCA’s final rules from accounting periods beginning on or after 1 January 2027.

How ESOS energy data serves those disclosures is on ESOS and UK SRS, and the reporting practice on UK SRS reporting guidance.

The sister reference covers the practical route in its ESOS Phase 4 compliance guide.

ESOS Phase 4: questions people ask

When is the ESOS Phase 4 qualification date?

The qualification date for Phase 4 is 31 December 2026.

It comes from regulation 4 of the ESOS Regulations 2014: the date is the 31 December immediately before the compliance date of 5 December 2027.

An undertaking that is a relevant undertaking on that date is in Phase 4, and a later change of size or structure does not take it out.

What are the ESOS qualification criteria for Phase 4?

An undertaking qualifies if it employs at least 250 persons, or if its annual turnover is in excess of £44 million and its annual balance sheet total is in excess of £38 million.

Schedule 1 paragraph 1 of the Regulations sets the test and paragraph 1A the amounts.

A small or medium undertaking also takes part if it is a group undertaking of a large one.

The thresholds did not change for Phase 4.

Does meeting only the turnover threshold bring you into ESOS?

No. The two money limbs are joined by "and": turnover in excess of £44 million and a balance sheet total in excess of £38 million.

Exceeding one of them is not enough.

The employee limb, at least 250 persons, works on its own.

How are employees counted for ESOS?

Schedule 1 paragraph 10 uses a monthly average: the number employed in each month of the accounting period used for the financial figures, added up and divided by the number of months.

Employees, owner managers and partners all count (paragraph 9). It is not a headcount taken on 31 December.

Which accounts are used for the ESOS Phase 4 financial test?

The accounts for the financial year ending on, or in the 12 months immediately before, 31 December 2026 (Schedule 1 paragraph 5).

For a company with a 31 December year-end that is the year ending 31 December 2026 itself.

What is the ESOS Phase 4 deadline?

The compliance date is 5 December 2027.

By then the responsible undertaking must notify the scheme administrator, through the Notification System the Environment Agency runs as MESOS, that the participant has complied.

The action plan follows by 5 December 2028, with progress updates due by 5 December 2029, 2030 and 2031.

What are the ESOS Phase 4 requirements?

Calculate total energy consumption over a 12-month reference period; cover at least 95% of it by an energy audit or an ISO 50001 certificate; calculate an energy intensity ratio for each organisational purpose; appoint a lead assessor unless an exemption applies; produce the ESOS report, which in Phase 4 includes the energy savings achieved and a review of the last action plan; have one or two responsible officers confirm it; and notify by 5 December 2027.

Is there a penalty for missing an ESOS action plan?

Not directly.

Part 8 of the Regulations lists five civil penalties and none of them names regulation 34A (the action plan) or regulation 34B (progress updates).

The Environment Agency says it will not take enforcement action for non-submission, and publishes the failure instead.

If a regulator served an enforcement notice requiring the plan, ignoring that notice would carry the regulation 46 penalty.

Does a company with an overseas parent qualify for ESOS?

It can.

The Environment Agency guidance treats UK groups that share an overseas parent as one corporate group for qualification: if one of them contains a large undertaking, all of them must take part, though each highest UK parent group participates separately by default.

An overseas undertaking with a UK establishment employing 250 people in the UK qualifies in its own right.

What was the ESOS Phase 3 qualification date?

The Phase 3 qualification date was 31 December 2022, the 31 December immediately before the Phase 3 compliance date.

The Phase 3 compliance date was extended to 5 June 2024.

Regulation 4 generates each phase from the same formula, which puts Phase 5 at 31 December 2030 and 5 December 2031.

What is the ESOS action plan deadline for Phase 4?

The action plan is due by 5 December 2028, one year after the compliance date, and covers 6 December 2027 to 5 December 2031.

Three progress updates follow, by 5 December 2029, 2030 and 2031 (regulations 34A and 34B).

Neither is named in the penalty table in Part 8, so no penalty attaches to missing them, although the Environment Agency publishes the failure.

How long must ESOS records be kept?

Regulation 28(2) requires the evidence pack to be kept for at least two compliance periods after the one it relates to.

For Phase 4 that is until at least 5 December 2035.

SI 2026/701 widened what the pack must hold, including the data behind every estimate.

When will ESOS Phase 4 notification data be published?

Regulation 10(2) requires publication within six months beginning with the compliance date, which on a literal count is 4 June 2028.

The Environment Agency announces 10 June 2028 for Phase 4.

The two are recorded side by side because nothing in either source says which counting convention applies.

Notification itself is free.

Does an undertaking with no energy use still have to notify?

Yes, if it qualifies.

Regulation 33A spares a qualifying undertaking with zero energy consumption the assessment, but it must still notify, with two directors confirming it has no energy responsibility.

Qualification turns on size, not on consumption.

Did SI 2026/701 change the ESOS thresholds?

No. The ESOS (Amendment) Regulations 2026 amend many provisions but do not touch regulation 15 or Schedule 1, so the 250, £44 million and £38 million limbs are unchanged since the euro figures were converted to sterling from 31 December 2020.

What is ESOS Phase 4?

Phase 4 is the fourth ESOS compliance period, running from 6 December 2023 to 5 December 2027.

Qualification is judged on 31 December 2026, the notification of compliance is due by 5 December 2027, and the action plan follows by 5 December 2028 according to the Environment Agency’s guidance.

Has the ESOS Phase 4 deadline been extended?

No. SI 2026/701 did not amend regulation 4, so the Phase 4 compliance date is still 5 December 2027, and the Environment Agency’s guidance says the regulators cannot amend it.

The only compliance date moved in recent years was Phase 3’s, which the guidance says was extended for six months to 5 June 2024.

What is the ESOS reporting period?

Regulation 22(5) says the reference period is 12 consecutive months that begin no more than 12 months before the qualification date and end on or before the compliance date.

For Phase 4 that means it begins no earlier than 31 December 2025 and ends by 5 December 2027.

The Environment Agency’s guidance, section 4.4, adds that it must include the qualification date and end before the compliance date; that is the Agency’s wording, not the regulation’s.

Who needs to do ESOS?

Any large undertaking in the UK, any small or medium undertaking that is a group undertaking of a large one, and every UK member of such a group, unless it is a public body or in insolvency proceedings between the qualification date and the compliance date.

Large means at least 250 persons, or turnover in excess of £44 million and a balance sheet total in excess of £38 million.

How often must companies undertake ESOS energy audits?

Once in each four-year compliance period.

A participant carries out an assessment, by audit or ISO 50001, for each phase it qualifies in, and qualification is re-tested on the 31 December before each compliance date: 31 December 2026 for Phase 4 and 31 December 2030 for Phase 5.

What data can a Phase 4 ESOS audit use?

Regulation 26(4)(b) bounds the 12-month data period: it begins no more than 12 months before the start of the compliance period, so not before 6 December 2022, and no more than 24 months before the audit starts, and it ends on or before 5 December 2027.

The Environment Agency’s guidance, section 8.3, states the same two floors.

What changed for ESOS Phase 4?

SI 2026/701, in force from 22 July 2026, removed Display Energy Certificates and Green Deal assessments as routes, widened the ISO 50001 route to total or significant consumption, added the savings achieved and the action plan review to the report, added a third progress update, and gave lead assessors a seven-day notification duty.

It left the size thresholds and the dates in regulation 4 alone.

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.

Checked against 51 sources fromlegislation.gov.ukEUR-LexEnvironment AgencyEnvironment Agency / GOV.UKDepartment for Environment, Food & Rural AffairsDepartment for Business and Trade

legislation.gov.uk
ESOS 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.uk
ESOS Regulations 2014, regulation 4 — compliance periods, qualification and compliance dates
The formula that generates 6 December 2023 – 5 December 2027, 31 December 2026 and 5 December 2027.
legislation.gov.uk
ESOS Regulations 2014, regulation 15 — relevant undertakings
A large undertaking, or a small or medium undertaking that is a group undertaking of one, on the qualification date.
legislation.gov.uk
ESOS Regulations 2014, regulation 16 — excluded undertakings
Public bodies (Procurement Act 2023 definition since 24 February 2025) and the insolvency exclusions widened on 22 July 2026.
legislation.gov.uk
ESOS 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.uk
ESOS Regulations 2014, regulation 2 — interpretation
“Undertaking” and “group undertaking” take their Companies Act 2006 meaning; “employee” its Employment Rights Act 1996 meaning; the four organisational purposes.
legislation.gov.uk
ESOS Regulations 2014, regulation 6 — compliance bodies
The regulators by nation, and the Secretary of State offshore. Not the group rule.
legislation.gov.uk
ESOS Regulations 2014, regulation 22 — total energy consumption and the reference period
Reference period begins no more than 12 months before the qualification date and ends on or before the compliance date (reg 22(5)).
legislation.gov.uk
ESOS Regulations 2014, Part 4 Chapter 3 (regulations 26–27) — the energy audit
Audit data window (reg 26(4)), site visits (26(3A)), audit records (26(9)) and what an audit must identify and estimate (reg 27).
legislation.gov.uk
ESOS 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.
legislation.gov.uk
ESOS 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.uk
The 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.uk
SI 2014/1643, introductory text — made 24 June 2014 under European Communities Act 1972 s.2(2)
legislation.gov.uk
The 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.uk
The 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.uk
SI 2026/701, regulation 28 — the third progress update (new reg 34B(1)(c))
legislation.gov.uk
Energy 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).
EUR-Lex
Directive 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.
legislation.gov.uk
Companies Act 2006, section 1162 — parent and subsidiary undertakings
The group definition ESOS borrows (with ss.1158–1161).
Environment Agency
How 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 Agency
Comply with the Energy Savings Opportunity Scheme (ESOS) phase 4 — publication page
Environment Agency / GOV.UK
Energy 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 Agency
Comply with the Energy Savings Opportunity Scheme (ESOS) — the earlier guidance collection
Serves the Phase 3 material. Not a source for any Phase 4 figure.
Environment Agency
Enforcement and sanctions policy (the policy root)
Publication of penalties: name, requirement breached, amount.
Environment Agency
The Environment Agency — scheme administrator (reg 5)
Department for Environment, Food & Rural Affairs
Greening government commitments 2021 to 2025
The separate framework for central government departments.
legislation.gov.uk
SI 2018/1155 — the instrument that created SECR
A different regime with a different test.
Department for Business and Trade
UK Sustainability Reporting Standards: UK SRS S1 and UK SRS S2
Published 25 February 2026; voluntary for any entity.
ISO
ISO 50001 — Energy management
The management-system standard behind the deemed-compliance route.
legislation.gov.uk
ESOS Regulations 2014, regulation 10(2) — publication of notified information
Six months beginning with the compliance date; the Environment Agency announces 10 June 2028.
legislation.gov.uk
ESOS Regulations 2014, regulation 25C — energy intensity ratios
At least one per organisational purpose; none where that purpose’s consumption is zero.
legislation.gov.uk
ESOS Regulations 2014, regulation 27A — the ESOS report
Produced before the compliance date, for each assessment, since Phase 3.
legislation.gov.uk
ESOS Regulations 2014, regulation 28(2) — the evidence pack
Kept for at least two subsequent compliance periods: for Phase 4, to at least 5 December 2035.
legislation.gov.uk
SI 2026/701, regulation 20 — notification tables for the deemed-compliance routes
Inserts regulation 29(1)(ad), (ae) and (af).
legislation.gov.uk
ESOS Regulations 2014, regulation 33A — zero energy consumption
Spares the assessment, not the notification.
legislation.gov.uk
SI 2018/1342 — ESOS (Amendment) (EU Exit) Regulations 2018
Where the sterling figures came from, for qualification dates on or after 31 December 2020.
legislation.gov.uk
SI 2015/1731 — ESOS (Amendment) Regulations 2015
Inserted “in excess of” before the balance-sheet amount, 26 October 2015.
legislation.gov.uk
Companies Act 2006, section 474(1) — meaning of “turnover”
Taken into Schedule 1 ¶4 with “undertaking” for “company”.
legislation.gov.uk
Employment Rights Act 1996, section 230(1) — meaning of “employee”
Taken into the ESOS Regulations by regulation 2.
legislation.gov.uk
Procurement Act 2023, section 2 — “public authority”
The public-body definition regulation 16 uses since 24 February 2025.
Department for Energy Security and Net Zero
The 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.
DESNZ / GOV.UK
Energy audits and reporting research, including the Energy Savings Opportunity Scheme
The research collection behind the post-implementation reviews.
Environment Agency
Energy Savings Opportunity Scheme — dataset (National Data Library)
The published notification data; updated 21 August 2026.
CIBSE Certification
ESOS Lead Assessors — an approved lead assessor register
One of the registers a lead assessor is drawn from.
BSI
PAS 51215-1:2025 — energy and decarbonisation assessment process specification
Voluntary; named in the Environment Agency hub.
UKAS
United Kingdom Accreditation Service
The national accreditation body, which accredits certification bodies.
Department for Energy Security and Net Zero
Environmental reporting guidelines, including Streamlined Energy and Carbon Reporting
The SECR guidance — a different regime with a different test.
Environment Agency
Comply with the Energy Savings Opportunity Scheme (ESOS): phase 3
Updated 30 July 2026; the Phase 3 deadlines, including the second progress update on 5 December 2026.
legislation.gov.uk
ESOS Regulations 2014, regulation 34A — action plans
Contents, estimate basis, the statutory window and notification through the Notification System.
Environment Agency
Manage your ESOS reporting (MESOS)
The online Notification System; launched in April 2024 for Phase 3.
NetRegs (SEPA, NIEA, Environment Agency)
Energy Saving Opportunities Scheme (ESOS)
Devolved summary. It says “more than 250 people”; Schedule 1 says at least 250, so the Regulations govern.

ESOS Phase 4: the thresholds and requirements, as the Regulations write them

What ESOS is, in the Regulations’ own terms

ESOS regulations: one scheme, three instruments

Who needs to do ESOS, and how often

Qualification: who is in on 31 December 2026

The ESOS thresholds, limb by limb

Who counts as employed

Which accounts

One large undertaking brings in the UK group

Acquisitions, disposals and reorganisations

Part of the group on the qualification date

Outside the seller’s group for Phase 4

Still complies, three ways

Its energy need not be added

Each part stays a group undertaking

Who is out of scope, and who only looks it

ESOS Phase 4 requirements, provision by provision

Find the participant

Total energy consumption

Significant energy consumption

Energy intensity ratios

Appoint a lead assessor

The energy audit

The ESOS report

Responsible officer sign-off

Notify

Keep the evidence pack

Action plan and progress updates

Two routes to compliance, and the ones that closed

What changed in ESOS Phase 4, on one toggle

ESOS Phase 4 deadlines, from qualification to the last update

ESOS Phase 3 qualification date and deadlines

Has the ESOS deadline been extended? The Phase 4 date, checked

The ESOS reporting period: what the regulation says, and what the guidance adds

The windows inside those dates

The Phase 4 ESOS audit: which data it can use

The ESOS action plan deadline: Phase 3 and Phase 4

What Phase 3 shows about participation

The penalty table, and the gap in it

Common qualification mistakes, each against its provision

ESOS beside SECR and UK SRS

Further reading from the authorities

How to comply with ESOS phase 4

ESOS: find out if you qualify and how to comply

SI 2026/701 as made

Second post-implementation review

Environmental reporting guidelines, including SECR

PAS 51215-1:2025

ESOS Phase 4: questions people ask

Primary sources

Read next

ESOS compliance, step by step

ESOS penalties

ESOS Phase 3 vs Phase 4