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Section · the Energy Savings Opportunity Scheme
ESOS guidance starts with one fact: the Energy Savings Opportunity Scheme Regulations 2014 require large UK undertakings and their groups to assess their energy use every four years.
Phase 4 is the current cycle; qualification is judged on 31 December 2026 and the notification is due by 5 December 2027.
Pick the question you came with below, watch the dates count down, and follow each answer to the provision it comes from.
The whole scheme in one line
Measure what you use, cover 95% of it, notify, then plan.
Everything below takes one of those verbs and follows it to the regulation that imposes it.
Start with your question
Nine questions cover most searches for ESOS compliance, reporting, regulations and guidance.
Each card names the provision it rests on and links to the page that goes further.
Sources: SI 2014/1643 Schedule 1, reg 4, Part 8, Environment Agency Phase 4 guidance.
Dates
ESOS dates come from a formula in regulation 4, not from a published calendar.
Each compliance period begins on 6 December and ends on 5 December four years later, and its qualification date is 31 December of the year before it ends.
So Phase 3 was judged on 31 December 2022, and its compliance date of 5 December 2023 was extended by six months to 5 June 2024.
Phase 4 is judged on 31 December 2026, runs from 6 December 2023, and has a compliance date of 5 December 2027.
The Phase 3 action plan cycle is still running: its second progress update is due by 5 December 2026.
The Environment Agency’s guidance puts the Phase 4 action plan at 5 December 2028, and says the regulators cannot amend the compliance deadline (Phase 4 guidance §§13.1, 15.1).
Dates in the right-hand panel before this one were counted as at 1 October 2026, and update in your browser once the page loads.
Counted as at 1 October 2026
Counted in your browser from today’s date; nothing is stored or sent.
Phase 3 and Phase 2
Searches for ESOS Phase 3 are searches for a cycle that has closed and one date that has not.
Follow the line from the 2019 compliance period to the second progress update on 5 December 2026.
The Phase 3 qualification date was 31 December 2022, the 31 December immediately before the formula compliance date of 5 December 2023.
The Environment Agency’s guidance says that compliance date was extended for six months to 5 June 2024, and that the fourth compliance period nevertheless began on 6 December 2023 (Phase 4 guidance §3).
Phase 3 was the first with action plans, added by SI 2023/1182, and its plans were due by 5 December 2024 under regulation 34A(7)(a).
Phase 3 participants should read the Agency’s own Phase 3 guidance, which it updated on 30 July 2026.
Phase 2 ran from 6 December 2015 to 5 December 2019, with a qualification date of 31 December 2018, and Phase 1 qualified on 31 December 2014 and complied by 5 December 2015.
Sources: reg 4, Part 6A, SI 2023/1182, EA Phase 3 guidance.
The cycle
Each phase has a qualification date, a compliance period and a compliance date.
Phase 3’s action plan cycle is still running while Phase 4’s assessment is under way.
| Phase | Qualification date | Compliance period | Compliance date |
|---|---|---|---|
| 1 | 31 Dec 2014 | 17 Jul 2014 – 5 Dec 2015 | 5 Dec 2015 |
| 2 | 31 Dec 2018 | 6 Dec 2015 – 5 Dec 2019 | 5 Dec 2019 |
| 3 | 31 Dec 2022 | 6 Dec 2019 – 5 Dec 2023 | 5 Jun 2024 (extended) |
| 4 | 31 Dec 2026 | 6 Dec 2023 – 5 Dec 2027 | 5 Dec 2027 |
| 5 | 31 Dec 2030 | 6 Dec 2027 – 5 Dec 2031 | 5 Dec 2031 |
Phase 4 changes, made by SI 2026/701 from 22 July 2026, are set out on ESOS Phase 3 vs Phase 4.
The Phase 5 dates in the table are the Environment Agency’s, and follow from the same regulation 4 formula.
In one screen
ESOS is an energy assessment scheme, not an emissions standard and not a target.
A participant measures its total energy consumption over twelve months, has at least 95% of it examined by an energy audit or covered by an ISO 50001 system, and records the cost-effective savings it could make.
A responsible officer confirms the work, and the participant notifies the regulator by the compliance date.
A year later it files an action plan, then progress updates against it, all published.
The test for who is in is Schedule 1: at least 250 persons, or turnover in excess of £44 million and a balance sheet in excess of £38 million, and every UK member of a group that contains such an undertaking.
The full test, with the counting rules, is on ESOS Phase 4 thresholds and qualification criteria.
Phase 4, in statutory order
ESOS compliance is a sequence, and each step produces the evidence the next one needs.
Scroll the route: each stop gives the Phase 4 duty, its provision and its date.
Qualification is a snapshot on 31 December 2026, taken from the accounts for the financial year ending on, or in the 12 months before, that date.
A large undertaking employs at least 250 persons, or has turnover in excess of £44 million and a balance sheet total in excess of £38 million.
A small or medium undertaking in the same group as a large one is in too.
Sch 1 ¶¶1, 1A, 5 · regs 15–17
250 persons at least, or over £44m turnover and £38m balance sheet
Total energy consumption is calculated over a reference period of 12 consecutive months.
The period begins no more than 12 months before the qualification date and ends on or before the compliance date, so for Phase 4 it can begin no earlier than 31 December 2025 and must end by 5 December 2027.
The unit may be kWh or spend; carbon dioxide is not an energy unit.
reg 22(5) · EA guidance §4
12 months consecutive, within the bounds of regulation 22(5)
The energy audit must cover assets and activities that together account for not less than 95% of total energy consumption.
The other route is ISO 50001 certification covering total or significant energy consumption, issued on or after 6 December 2023 and valid on 5 December 2027.
Display Energy Certificates and Green Deal Assessments stopped being routes from Phase 4.
reg 25(2) · reg 33 · SI 2026/701 regs 24, 26
95% of total energy consumption, regulation 25(2)
ESOS has four organisational purposes: transport, industrial processes, buildings and any other purpose.
At least one energy intensity ratio is required for each purpose, and none where that purpose’s consumption is zero.
Since 22 July 2026 the quantifiable factor must rest on verifiable data where reasonably practicable, or on a reasonable estimate.
reg 2(1) · reg 25C
4 organisational purposes, one ratio at least for each
A lead assessor from an approved register must oversee the assessment.
None is required where total energy consumption is less than 40,000 kWh, or where ISO 50001 certification covers total or significant consumption.
The assessor must tell their approval body within seven days of completing the assessment.
reg 21(2A), (3) · reg 12
40,000 kWh below this no lead assessor, regulation 21(3)
The ESOS report is produced for every assessment, and from Phase 4 it records the savings actually achieved, in kWh, and an action plan review of measures not carried out.
The evidence pack is kept for at least two further compliance periods, which for Phase 4 means until at least 5 December 2035.
regs 27A, 27D, 27E · reg 28(2)
2 further compliance periods the evidence pack is kept
The responsible officer confirms the compliance steps, and the participant notifies the Environment Agency through the Notification System.
The Environment Agency says notification is free and that the regulators cannot amend the deadline.
Even a participant with no energy consumption must still notify.
regs 29–31 · reg 33A
The Environment Agency’s guidance says the Phase 4 action plan is due by 5 December 2028 and covers 6 December 2027 to 5 December 2031, with savings stated in kWh.
Three annual progress updates follow, owed even where the plan proposed no measures.
The Phase 4 updates fall in the three years ending 5 December 2029, 2030 and 2031.
reg 34A(7) · reg 34B(1)
3 annual progress updates after the plan
Three things are new in Phase 4: the report records savings actually achieved, it includes a review of measures from the last action plan that were not carried out, and there are three progress updates, not two.
Display Energy Certificates and Green Deal Assessments are gone as routes, and the lead assessor now owes a personal seven-day notification (SI 2026/701 Explanatory Note).
Neither UK ETS nor a climate change agreement counts as ESOS compliance, though their data can feed the calculation; the Environment Agency’s guidance says additional work is likely.
ESOS compliance takes each step in turn, with the evidence each produces.
The audit
An ESOS energy audit is judged by what it hands back, and regulation 27 lists it.
Choose a stage to read what it asks for and where the Regulations say so.
Regulation 26 requires the audit to rest on verifiable data over 12 months, and the amended text asks for site visits representative of how energy is used (regulations 26–27).
The audit covers buildings, industrial processes and transport, and it is overseen by a lead assessor unless an exemption applies.
ISO 50001 certification is the other route, and the audit page and the ISO 50001 page set the two side by side.
ESOS energy audits goes through data windows, site visits and what the assessor records.
The audit boundary
Regulation 25(2) asks for assets and activities that together account for not less than 95% of total energy consumption, measured in energy units or by spend (regulation 25).
The figure was 90% until SI 2023/1182 raised it on 29 November 2023.
For ISO 50001 the Phase 4 test is total or significant energy consumption, and significant means at least 95%.
The guidance lets you classify whichever activities you choose as the de minimis remainder.
Audit data has two floors: it must begin no earlier than 6 December 2022, and no earlier than 24 months before the audit starts, so a late audit cannot reach back to 2022 data (Phase 4 guidance §8.3).
The reference period for total consumption is separate and is set by regulation 22(5).
Where total energy consumption is less than 40,000 kWh, no lead assessor is needed (regulation 21(3)); the boundary tool further down shows how that differs from SECR’s line.
When does the audit start?
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.
The bounds on the data period, not advice on which period to choose.
Reporting
ESOS reporting is one chain from the meter to a published notification, and each link leaves evidence.
The chain ends in a pack that must be kept until at least 5 December 2035.
The ESOS report is produced for each assessment, an obligation introduced for Phase 3 by regulation 27A.
In Phase 4 the report states the energy savings actually achieved in the compliance period, in kWh, measure by measure, under SI 2026/701 regulation 17.
Only the combined saving is published, and the review of measures not implemented in the last plan is not.
The evidence pack is kept for at least two further compliance periods under regulation 28(2), and now holds the data behind every estimate.
Sources: regs 22, 25, 25C, 27A, 28, 29, 30 and SI 2026/701 regs 17, 18.
Notification
The notification of compliance is the one filing every Phase 4 participant owes.
The responsible officer confirms the steps taken, and the guidance says one director signs off where the lead assessor is external and two where the lead assessor is internal or none was appointed (regulation 30).
Regulation 10(2) requires publication of notified information within six months beginning with the compliance date, which on a literal count is 4 June 2028, while the Agency announces 10 June 2028 (regulation 10).
The Agency publishes the notification data as an open dataset, and nothing read says which counting convention it uses.
Participants relying on ISO 50001 still notify, and regulation 29(1)(ad) to (af) add the information the notification carries for the deemed-compliance routes.
| Question | Answer | Source |
|---|---|---|
| Where | The Notification System, run by the Environment Agency as MESOS | MESOS |
| When | After 31 Dec 2026 and by 5 Dec 2027 | reg 29 |
| Cost | Free, says the guidance | EA §12.1 |
| Amend the date | Regulators cannot, says the guidance | EA §15.1 |
| Zero energy | Still notifies | reg 33A |
| Published | Name, requirement breached and amount, for penalties; notified data on a date | reg 10 |
After the notification
The action plan is the filing that searches for ESOS deadlines, guidance, submission and templates keep asking about.
Seven dates sit on one line below, across both phases.
Regulation 34A(3) says a plan lists each energy efficiency measure the participant proposes to implement, whether an audit recommended it, the date and the expected saving in kWh, or states that there is no such measure (regulation 34A).
The plan is submitted through the Notification System, and this page does not publish a template because the system collects the contents.
A progress update reports what has been done against the plan, and Phase 4 has three, because regulation 28 of SI 2026/701 added a third and final update.
Part 8 names neither the plan nor an update, so no penalty attaches to missing them, although the Agency publishes the failure.
The action plan page sets out the contents and windows in full.
People
A lead assessor is an individual on an approved register who oversees the ESOS assessment.
GOV.UK lists seven approved registers kept by professional bodies, such as CIBSE Certification’s, and the list is versioned and has changed without notice.
The competence standard the Regulations still name is PAS 51215:2014, and the 2025 PAS 51215-1 and -2 are voluntary.
A lead assessor must notify their approval body within seven days of completing an assessment, naming two contacts at the participant (regulation 21(2A)).
The exemptions are the three on the tool beside this text: zero consumption, an ISO 50001 certificate over total or significant consumption, and consumption less than 40,000 kWh.
Measuring
Total energy consumption sets the size of everything else, including the 95% line.
These six rules come from regulation 22 and the Environment Agency’s guidance, labelled as guidance where they are.
Qualification
The figures come from the accounts for the financial year ending on, or in the 12 months before, the qualification date (Schedule 1 ¶5).
For a company with a 31 December year end, Phase 4 therefore uses the 2026 accounts, not 2025.
Headcount is not a year-end count: it is the total of persons employed in each month of the accounting period, divided by the number of months.
Employees, owner managers and partners all count.
Once large, an undertaking stays large until it has been small or medium for two consecutive accounting periods.
The drafting is asymmetric: “at least” 250 persons, but “in excess of” the money limbs, so exactly 250 employees qualifies and exactly £44 million of turnover does not.
A group complies as one participant through its highest UK parent (regulation 17), and a small or medium member of a large group is a relevant undertaking in its own right (regulation 15(1)(b)), with the Companies Act group definition in section 1162.
Public bodies are out, now by the Procurement Act 2023 definition, and so is any undertaking in insolvency proceedings at any point between the qualification date and the compliance date (regulation 16).
The check beside this text runs those rules on your own figures and reads nothing else.
Phase 4 check · one undertaking at a time
Figures for the accounting period ending on, or in the 12 months before, 31 December 2026.
Your 12-month reference 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 §4.4Indicative, 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.
The regulators
The Environment Agency is the scheme administrator for the whole UK: it writes the guidance, runs the helpdesk and collects notifications.
Enforcement falls to the regulator where the undertaking’s registered office is, under regulation 6.
The Department for Energy Security and Net Zero owns ESOS policy: the consultations, the government responses and the amending Regulations.
So “DESNZ guidance” is the wrong label for either of the two guidance documents, which are the Environment Agency’s.
Notifications go through the Notification System, which the Environment Agency runs as MESOS, launched in April 2024 for Phase 3.
The helpdesk is esos@environment-agency.gov.uk.
| Registered office | Regulator |
|---|---|
| England | Environment Agency |
| Wales | Natural Resources Wales |
| Scotland | Scottish Environment Protection Agency |
| Northern Ireland | Northern Ireland Environment Agency |
| Wholly or mainly offshore | Secretary of State, DESNZ |
The law
ESOS regulations are one instrument, SI 2014/1643, amended by SI 2023/1182 and SI 2026/701.
Search or filter the table, and read the Phase 4 change against the 2014 provision it amends.
| Sch 1 | The large undertaking test: at least 250 persons, or turnover over £44m and balance sheet over £38m | Unchanged |
| reg 4 | Compliance periods, qualification dates and compliance dates for every phase | Unchanged; yields 31 Dec 2026 and 5 Dec 2027 |
| reg 5 | The scheme administrator: the Environment Agency, for the whole UK | Unchanged |
| reg 6 | The compliance bodies by nation, and the Secretary of State offshore | Unchanged |
| regs 15–17 | Relevant undertakings, exclusions, participants and the highest parent group | Reg 16(1)(c) inserted by SI 2026/701 reg 6; insolvency limb widened |
| reg 21 | The lead assessor, the 40,000 kWh limb and the seven-day notification | Reg 21(2A) new |
| reg 22 | Total energy consumption and the 12-month reference period | Phase 4 period follows from reg 4; read the 2014 text |
| regs 25, 25C | The 95% line and the energy intensity ratios | Reg 25B(4) and 25C(4) inserted (SI 2026/701 regs 10, 11) |
| regs 26–27 | The energy audit: data, site visits, opportunities, payback | Reg 26(1) words substituted (SI 2026/701 reg 12) |
| regs 27A, 27D, 27E | The ESOS report, savings achieved and the action plan review | Savings and review new (Chapter 3B) |
| regs 33, 33A | Deemed compliance through ISO 50001, and zero energy consumption | Reg 33(2A) and reg 33A inserted (SI 2026/701 regs 24, 25) |
| reg 10 | Publication of notified information within six months of the compliance date | Unchanged |
| reg 28 | The evidence pack and how long it is kept | Reg 28(1)(a)(iv)–(ix), (j), (k) inserted (SI 2026/701 reg 18) |
| regs 29–31 | Notification of compliance and the responsible officer’s confirmation | Reg 29(1)(ad)–(af) inserted (SI 2026/701 reg 20) |
| regs 34A, 34B | The action plan and the progress updates | Reg 34A(11), 34B(1)(c) and 34B(9) inserted (SI 2026/701 regs 27, 28) |
| regs 43–47 | The five civil penalties and publication | Part 8 names neither 34A nor 34B |
16 of 16 rows
Provisions of SI 2014/1643; Phase 4 changes from legislation.gov.uk’s list of changes yet to be applied, read 1 October 2026, and SI 2026/701.
legislation.gov.uk’s consolidation of the 2026 amendments is only partial, so a Phase 4 citation names the 2014 provision and the regulation of SI 2026/701 that changed it.
The legislation began as the UK’s implementation of the energy audit requirement of the Energy Efficiency Directive 2012/27/EU, and the live amending power is now the Energy Act 2023.
The official guidance
ESOS has more official material than most regimes, and it does not all agree.
The instrument outranks every restatement of it.
| Document | What it is | Use it for |
|---|---|---|
| SI 2014/1643, the ESOS Regulations | The law | Every duty, threshold, date and penalty. Consolidation of the 2026 amendments is partial. |
| SI 2026/701 | The law, Phase 4 changes | Read beside the 2014 text for any Phase 4 provision. |
| EA Phase 4 guidance | Regulator restatement, 30 July 2026 | Practical detail on groups, transport and estimates. Contradicts itself on the number of progress updates. |
| GOV.UK ESOS overview | Regulator summary, rewritten 2 September 2026 | The approved lead assessor registers and the voluntary net zero standards. |
| EA Phase 3 guidance | Phase 3 only, updated 30 July 2026 | The remaining Phase 3 deadline: the second progress update. |
| Enforcement policy, Annex 2 | How penalties are set | The four-step calculation and the ESOS worked example. |
| Earlier guidance collection | Phase 3 only | Useful for the Phase 3 action plan cycle; not for Phase 4. |
| NetRegs ESOS page | Devolved summary | A starting point in Scotland and Northern Ireland. Check any threshold against Schedule 1. |
Where the guidance and the law part company
A page that copies the guidance repeats its slips.
Every figure here is read from the instrument first.
How to treat groups with overseas parents, franchises, trusts and joint ventures.
Which transport fuel is yours, and how to estimate.
Sources: reg 22(5), Part 6A, SI 2026/701 reg 28, Sch 1 ¶1, EA Phase 4 guidance, NetRegs.
Checking
Some statements about ESOS are repeated widely and do not match the Regulations.
Each card gives the claim as it circulates, and the provision that answers it.
The reference
| Your question | Go to | What it covers |
|---|---|---|
| Am I in Phase 4? | ESOS Phase 4 thresholds | The thresholds and qualification criteria, read from Schedule 1, with a checker. |
| Is ESOS mandatory? | Is ESOS mandatory? | What the law compels, under which power, and which duties carry a sanction. |
| What do I do, in what order? | ESOS compliance | The Phase 4 duties in statutory sequence, and the evidence each produces. |
| What must the energy audit contain? | ESOS energy audits | Regulations 26 and 27: data windows, site visits, costs, payback. |
| Can ISO 50001 replace the audit? | ISO 50001 and ESOS | What regulation 33 deems, and what it never does. |
| What goes in the action plan? | The ESOS action plan | Regulations 34A and 34B: contents, windows, publication. |
| What if we miss it? | ESOS penalties | The Part 8 table and how the Environment Agency sets an amount. |
| What changed for Phase 4? | ESOS Phase 3 vs Phase 4 | SI 2026/701, row by row, and what it left alone. |
| How does ESOS feed UK SRS? | ESOS and UK SRS | ESOS data against SECR, UK SRS S2 and PPN 006. |
Enforcement
The five civil penalties are statutory, in Part 8, and each can carry a publication penalty.
None of them names the action plan.
| Regulation | Failure | Fixed maximum | Daily amount |
|---|---|---|---|
| 43 | To notify | £5,000 | £500 per working day, up to 80 |
| 44 | To keep records | £5,000, plus audit costs | None |
| 45 | To undertake an ESOS assessment | £50,000, or a lesser amount the regulator decides | £500 per working day, up to 80 |
| 46 | To comply with a compliance, enforcement or penalty notice | £5,000 | £500 per working day, up to 80 |
| 47 | False or misleading statement | £50,000, or a lesser amount the regulator decides | None |
Regulations 34A and 34B appear nowhere in Part 8, so non-submission of an action plan or progress update carries no penalty of its own.
The Environment Agency’s policy is to normally impose an initial penalty of up to £5,000, not £50,000, on a new entrant that fails to carry out an audit in the compliance period in which it first enters the scheme (Annex 2, section D2.3).
That is policy, not statute, and it does not apply in later periods.
Appeals go to the First-tier Tribunal in England, Wales and offshore, to the Scottish Ministers in Scotland, and to the Planning Appeals Commission in Northern Ireland (guidance §15.2).
The penalties page explains how an amount is set.
The evidence
The second post-implementation review, dated 18 July 2025, is the government’s own account of how ESOS is working.
It records that 8,581 corporate groups notified for Phase 3 against the 9,871 the Environment Agency believed qualified, and that 7,145 of those confirmed they were required to comply.
Of the groups that notified, 5,403 filed an action plan, and 4,716 of those plans contain at least one energy saving action.
The review calls these findings provisional, and recommends keeping the Regulations with no major changes until a full evaluation reports.
The Environment Agency also publishes the notification data as an open dataset, and says the 2023 reforms are estimated to add 28 TWh across all participants over 2024 to 2037 (a government estimate the Agency quotes from DESNZ).
Reform
People searching for the ESOS consultation are usually after one of two documents, and neither changes ESOS.
The first is Modernising corporate reporting, published on 7 September 2026, which proposes removing the directors’ report and does not change who must do ESOS.
Its paragraph 150 is the second: DESNZ intends to hold a consultation on SECR and ESOS later in 2026, exploring longer-term options to reform SECR.
That consultation is to build on the SECR evaluation of 29 January 2026 and on an ESOS evaluation the document describes as under way.
The 2025 review of ESOS itself recommended keeping the Regulations with no major changes.
When this page was last checked, on 1 October 2026, no consultation document on ESOS had been published, and none has a date.
Until one appears, ESOS applies exactly as the Regulations and the Phase 4 guidance describe.
The same promise covers SECR, whose scope is on the SECR thresholds page.
Beside ESOS
Many ESOS participants also report under SECR, an annual disclosure with its own test.
Choose a regime on the orbit to read how it differs, then try a number on the 40,000 kWh line.
Try a number against both lines
A lead assessor is needed: the exemption applies only below 40,000 kWh.
SI 2014/1643 reg 21(3): “less than 40,000 kWh”The UK energy-use relief applies: 40,000 kWh or less.
SI 2008/410 Sch 7 para 20D(7)(a): “40,000 kWh or less”Only the 40,000 kWh line is tested; the rest of each regime’s scope is separate.
The sharpest difference is that both regimes use 40,000 kWh, and a figure of exactly 40,000 gives opposite answers (SECR Schedule 7, ESOS regulation 21(3)).
The two regimes are compared on ESOS vs SECR and SECR thresholds.
The UK SRS side is covered on the UK SRS hub, the UK SRS timeline and the UK SRS compliance guide.
Software that holds the energy data once and serves all three is surveyed on carbon management software, and advisory routes on sustainability consultancy.
The sister reference’s ESOS Phase 4 compliance guide takes the practical route, and every section of this site is listed on all sections.
The government’s SECR guidance is the place to check the SECR side.
Further reading from the authorities
The law
The regulator
Evidence and standards
Frequently asked
ESOS, the Energy Savings Opportunity Scheme, is a UK scheme that requires large undertakings and their corporate groups to assess their energy use every four years, identify cost-effective ways to save energy, and notify the regulator that they have done so.
It is set up by the Energy Savings Opportunity Scheme Regulations 2014 and administered by the Environment Agency.
Energy Savings Opportunity Scheme.
The 2014 Regulations that created it were first made to implement the energy audit requirement of the EU Energy Efficiency Directive; since the Energy Act 2023 the amending powers are domestic, and SI 2023/1182 and SI 2026/701 were made under them.
An undertaking qualifies if, on the qualification date, it employs at least 250 persons, or has turnover in excess of £44 million and a balance sheet total in excess of £38 million, and so does every UK member of a corporate group that contains one.
Public bodies and undertakings in insolvency proceedings between the qualification date and the compliance date are excluded.
For Phase 4 the qualification date is 31 December 2026.
Yes, for an undertaking that is in scope: the ESOS Regulations 2014 are a statutory instrument, and Part 8 carries five civil penalties for breaches.
An undertaking below the size test, with no large group member, has no duty under it.
Yes.
Each compliance period runs from 6 December to 5 December four years later, and regulation 4 generates the qualification date and compliance date of every phase from that formula.
Phase 4 runs from 6 December 2023 to 5 December 2027, and Phase 5 from 6 December 2027 to 5 December 2031.
Phase 4, whose compliance period began on 6 December 2023, with qualification judged on 31 December 2026 and notification due by 5 December 2027.
Phase 3 is not finished: its participants owe a second progress update by 5 December 2026.
For Phase 3 participants, the second progress update on their action plan is due by 5 December 2026.
For Phase 4, qualification is judged on 31 December 2026 and the notification of compliance is due by 5 December 2027, with the action plan due by 5 December 2028 according to the Environment Agency’s guidance.
The Phase 3 compliance date was 5 December 2023 under the formula in regulation 4, and the Environment Agency’s guidance says it was extended for six months to 5 June 2024.
Phase 3 action plans were due by 5 December 2024, and the Agency accepted them until 5 March 2025.
Phase 3 introduced action plans, progress updates, the 95% line and the energy intensity ratios, through SI 2023/1182 from 29 November 2023.
Phase 4 adds savings achieved, a review of the last action plan, a third progress update and the ISO 50001 change, and drops Display Energy Certificates and Green Deal assessments as routes, through SI 2026/701 from 22 July 2026.
An ESOS energy audit is an audit of the energy use of buildings, industrial processes and transport, led by an approved lead assessor, that must cover assets and activities accounting for not less than 95% of total energy consumption. It identifies cost-effective energy saving measures.
The other route is ISO 50001 certification that covers the participant’s total or significant energy consumption.
Total energy consumption is measured in one common unit, either kWh or spend in pounds, and carbon dioxide is not an energy unit.
The Environment Agency’s guidance says all of the participant’s UK energy counts, whoever in the group holds the asset, that self-generated energy counts, and that in combined heat and power only the incoming fuel and mains electricity count.
Yes: transport is one of the four organisational purposes, with industrial processes, buildings and any other purpose.
The Environment Agency’s guidance, which is not law, treats as yours the transport fuel you are supplied with for business purposes.
An action plan records each energy efficiency measure the participant proposes to implement before the end of the relevant compliance period, whether an audit recommended it, the date it will be done and the kWh saving expected, or states that there is no such measure.
It is published by the Environment Agency, and progress updates then report what has actually been done against it.
Regulation 34A(3) sets out what a plan contains, and the plan is submitted through the Environment Agency’s Notification System rather than as a free-form document.
This page lists the contents; it does not publish a template, because the Notification System collects them.
A progress update reports what has been done against the action plan, in kWh, and is submitted through the Notification System on an annual window.
Phase 4 has three, due by 5 December 2029, 2030 and 2031, and they are owed even where the plan proposed no measures.
Through one of the seven approved registers that GOV.UK lists, kept by professional bodies; the individual joins a register, not the Environment Agency.
The competence standard the Regulations still name for Phase 4 is PAS 51215:2014.
Since 22 July 2026 a lead assessor must also notify their approval body within seven days of completing an assessment.
The Phase 3 assessment is finished: its compliance date was extended to 5 June 2024.
Its action plan cycle is not: Phase 3 participants owe a second progress update by 5 December 2026.
Phase 4 began on 6 December 2023, so the two overlap.
The Environment Agency published “How to comply with the Energy Savings Opportunity Scheme (ESOS) phase 4” on 30 July 2026, and rewrote the GOV.UK ESOS overview for Phase 4 on 2 September 2026.
Both restate the ESOS Regulations 2014 as amended; where they differ from the Regulations, the Regulations govern.
DESNZ has said it intends to consult on SECR and ESOS later in 2026, building on an evaluation of ESOS that is under way.
When this page was last checked, on 1 October 2026, no consultation document had been published, and the separate Modernising corporate reporting consultation does not change ESOS.
Yes.
ESOS applies across the UK.
The Environment Agency is the scheme administrator for the whole UK; the regulator follows the registered office — the Environment Agency, Natural Resources Wales, SEPA or the Northern Ireland Environment Agency — with the Secretary of State for wholly or mainly offshore undertakings.
The evidence pack must be kept for at least two compliance periods after the one it relates to.
The Phase 4 pack must therefore be kept until at least 5 December 2035, under regulation 28(2).
No. ESOS is a four-yearly energy assessment notified to the Environment Agency, with its own size test.
SECR is an annual energy and carbon disclosure in the directors’ report, with a different test.
Many large companies are in both, and the data overlaps, but neither satisfies the other.
Sources
Every figure, date and status on this page traces to the instrument’s owner.
Secondary commentary is never the source for a number.
In force 17 July 2014. Consolidation of the 2026 amendments is partial — read with SI 2026/701.
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).
The formula that generates 6 December 2023 – 5 December 2027, 31 December 2026 and 5 December 2027.
The Environment Agency administers the scheme for the whole UK.
The four national regulators and the Secretary of State offshore.
What the scheme administrator publishes and within six months of when.
A large undertaking, or a small or medium undertaking that is a group undertaking of one, on the qualification date.
Public bodies (Procurement Act 2023 definition since 24 February 2025) and the insolvency exclusions widened on 22 July 2026.
A highest parent group complies as one participant; parent undertaking in the Companies Act 2006 s.1162 sense.
The 40,000 kWh limb (reg 21(3)) and the lead assessor’s personal seven-day notification (reg 21(2A)).
Reference period begins no more than 12 months before the qualification date and ends on or before the compliance date (reg 22(5)).
Not less than 95% of total energy consumption, since 29 November 2023.
At least one ratio for each organisational purpose.
Audit data window (reg 26(4)), site visits (26(3A)), audit records (26(9)) and what an audit must identify and estimate (reg 27).
A Phase 3 introduction.
Kept for at least two further compliance periods: Phase 4’s to 5 December 2035.
What is notified, including the new limbs for the deemed-compliance routes.
The ISO 50001 route as amended by SI 2026/701.
No assessment and no lead assessor, but a notification is still owed.
Consolidated to 22 July 2026: contents, windows, kWh basis, the third progress update, the zero-energy carve-out.
The five penalties and publication; regulations 34A and 34B are named nowhere in Part 8.
In force 29 November 2023: the Phase 3 changes — action plans, the 95% line, site visits, intensity ratios.
Made 23 June 2026, in force 22 July 2026: the Phase 4 changes. Made under Energy Act 2023 ss.254–260 and 263.
The regulator-facing summary of the Phase 4 changes, including the removal of DECs and Green Deal Assessments.
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).
Published 30 July 2026. A restatement of the Regulations, never the source over them; where it and the SI differ, the SI governs.
Rewritten for Phase 4 on 2 September 2026; seven approved lead assessor registers; PAS 51215-1 and -2:2025 voluntary.
Updated 30 July 2026; the remaining Phase 3 deadline is the second progress update, 5 December 2026.
Phase 3 material, still online for Phase 3 participants.
The online Notification System; launched in April 2024 for Phase 3.
How the Environment Agency approaches enforcement across the schemes it runs.
Updated 10 October 2025. Step 3 bands and the ESOS worked example; §D2.3 new entrants.
The open dataset of Phase 3 action plans, progress updates and compliance notifications (updated 21 August 2026).
Devolved summary. It says “more than 250 people”; Schedule 1 says at least 250, so the Regulations govern.
¶19: 9,871 groups believed to qualify for Phase 3; 8,581 notified; 5,403 action plans. Recommendation: keep.
The collection that holds the 2020 and 2025 post-implementation reviews.
The evaluation of SECR that ¶150 says the ESOS and SECR consultation will build on.
Published 26 May 2026; recommends retaining SECR with amendments.
¶150: DESNZ intends to consult on SECR and ESOS later in 2026; an ESOS evaluation is under way.
The standard behind the certification route.
The UK national accreditation body; ISO 50001 certification must come from an accredited body (UKAS, an EU national body or an IAF member).
One of the seven approved registers; shown as an example of how a register describes its own scheme.
The group definition ESOS borrows (with ss.1158–1161).
A different regime: exceed at least two of £36m, £18m and 250 employees; the energy-use relief at 40,000 kWh or less (para 20D(7)(a)).
The SECR guidance, for the annual regime that sits beside ESOS.
Contents (reg 34A(3)), basis of estimates, window, notification through the Notification System.
The confirmation that accompanies the notification.
Inserts regulations 27D and 27E.
Continue reading
The qualification criteria on 31 December 2026, and everything owed by 5 December 2027.
The duties in the order the Regulations impose them.
What regulation 34A requires, and the three Phase 4 progress updates.