ESOS Phase 4: the compliance guidance

Every ESOS Phase 4 deadline, to December 2031

Statutory dates under SI 2014/1643 as amended by [2] SI 2023/1182 and [3] SI 2026/701 — from the opening of the compliance period to the third and final progress update.

Phase 3 versus Phase 4

The substantive Phase 4 changes, all confirmed by the Environment Agency’s guidance of 30 July 2026 [5]: DECs and GDAs removed, achieved savings reported, the previous action plan reviewed, and a third progress update added. Select a card for the detail.

One quiet removal travels with them — the requirement to state a payback period for each proposed measure is gone [3].

Phase 3 is not over yet

Two phases run at once through 2026 — and the next December deadline on this page is a Phase 3 one.

If you notified for Phase 3, your second progress update against the Phase 3 action plan is due 5 December 2026 [5] — twenty-six days before the Phase 4 qualification snapshot.

The practical consequence is one sentence long: keep the Phase 3 paper trail warm, because Phase 4 is the first phase that audits it. ESOS action plans covers both phases’ plan and update obligations in full.

Four phases, one scheme — and a deadline that moved once

ESOS has run in four-year cycles since [1] the ESOS Regulations 2014, made under the EU Energy Efficiency Directive and retained after exit. Anyone searching for “the ESOS deadline” is usually looking at the wrong phase’s date — this is all of them.

The Phase 3 extension is why so many pages still disagree about “the ESOS deadline” — and why every date on this page is cited to the instrument that set it, not to another guide.

ESOS Phase 4 guidance: the 30 July document, mapped

The Environment Agency’s How to comply with ESOS phase 4 is roughly 33,000 words across seventeen sections [5].

It is the primary source for this page — and almost every commercial page still ranking was written against the 2025 postponement and says Phase 4 guidance is “expected in early 2027”, which stopped being true on 30 July 2026.

Where each of its sections is answered on this page, and where the depth lives on this site:

Who is in, who is out — the edge cases

The 250-employee and £44m/£38m tests are the easy part. Phase 4 scope is decided at the boundaries — groups, insolvency, zero consumption, and where in the UK you are regulated [5].

Geography does not change scope, only the regulator: ESOS covers England, Wales, Scotland, Northern Ireland and offshore, with the Environment Agency as UK scheme administrator and the regulator following your registered office — NRW in Wales, SEPA in Scotland, NIEA in Northern Ireland, and DESNZ for wholly offshore activity [5].

The qualification test itself is unchanged by SI 2026/701 — alignment with SECR’s thresholds was considered and deferred to Phase 5 [3].

What counts as energy — and the 95% floor

Total energy consumption means everything your organisation used in the reference period across three headings — buildings, transport and industrial processes — converted to kWh [5].

Your assessment must then cover your significant energy consumption: the areas making up at least 95% of that total, a floor SI 2023/1182 raised from 90% [2].

The reference period is 12 consecutive months that include 31 December 2026 and end before 5 December 2027, using verifiable data wherever reasonably practicable [5].

Where you estimate, the guidance sets the method and the estimate must be identified as one — an audit built on unexplained estimates is the thing the evidence pack exists to prevent [5].

Three routes, one threshold

Energy audit, ISO 50001, or a combination — all three must reach the same 95% of total consumption [10]. Drag the slider to see which route you are actually on.

Two routes that worked in Phase 3 are gone: Display Energy Certificates and Green Deal Assessments no longer count — SI 2026/701 regulation 26 removes them, because they “provide more limited and less tailored recommendations than an ESOS energy audit” [3]. Their data may still feed your report; it can no longer be your route.

The ESOS energy audit, briefly

An ESOS energy audit is not a walk-round with a clipboard — since Phase 3 it must include representative site visits [2].

Its analysis runs across six energy-saving categories and four organisational purposes, and every opportunity it identifies carries an estimated saving in kWh [2][5].

Phase 3 audits identified 47 TWh of potential annual savings — about 5% of everything participants consume [9].

The government projects the 2023 strengthening alone will save participants 28 TWh and £1.12 billion in energy bills between 2024 and 2037 [5].

One distinction saves a lot of confused procurement: the assessment is the whole regulated exercise — measurement, audits, report, sign-off — while an audit is one technical input inside it [5]. Buying “an ESOS audit” does not, by itself, make you compliant.

What the audit must leave behind is as prescribed as the audit itself: an evidence pack the regulator can call for, holding the data, the sampling approach, the calculations and the opportunities identified [5].

Methodology, sampling and how to prepare are the ESOS energy audit guide’s job — this page only needs you to know the audit is the route most organisations take, and it ends in a named assessor’s sign-off.

The savings you actually achieved

Phase 4’s biggest structural change: the scheme stops asking only what you could save and starts asking what you did.

SI 2026/701 regulation 17 inserts a new Chapter 3B: the ESOS report and the notification of compliance must state the energy savings achieved during the compliance period [3].

Almost no page ranking for ESOS mentions this duty exists — it is the single clearest sign a guide was written before 22 July 2026.

The action plan, the review, and three more Decembers

Notification is not the end of Phase 4 — it opens a four-year reporting tail that runs to 5 December 2031 [4].

The action plan is due by 5 December 2028, covers 6 December 2027 to 5 December 2031, is signed off by a director, and is published by the Scheme Administrator [5].

Then three progress updates — 2029, 2030 and, new in Phase 4, 2031 [4].

There is no penalty for failing to submit an action plan or a progress update — the regulators have said they will not take enforcement action, and the Scheme Administrator publishes the failure instead [5]. The exposure is reputational, and it is by design.

Deadline calculators, the review structure and the MESOS field detail live on the ESOS action plan guide — the depth on plans and updates is that page’s job, for both Phase 3 and Phase 4.

Notifying through MESOS

MESOS — Manage your Energy Savings Opportunity Scheme reporting — is the Environment Agency system every Phase 4 notification, action plan and progress update goes through [5].

Before anything is submitted, one or more directors (or equivalent) must have reviewed and signed off the assessment — and the same sign-off duty applies to the action plan and every update [5].

The notification now carries the Phase 4 additions: the savings you achieved, and the review of your previous action plan [3][5].

What the Scheme Administrator then publishes: action plans, progress updates, the combined savings figure, and any compliance failure — but not your per-measure savings and not the action-plan review [5].

Submission mechanics and the evidence pack are covered in the ESOS reporting hub.

ESOS Phase 4 compliance, step by step

Fourteen steps from the qualification snapshot to submission — a working checklist you can tick through, built against the Environment Agency guidance’s own stages [5].

GOV.UK publishes no compliance checklist — the appendices to the Phase 4 guidance are checklists of what the report must contain, not of what you have to do [6]. A well-structured Phase 4 programme takes 12–18 months.

Find an approved lead assessor

Lead assessors must be registered with one of six Environment Agency-approved professional bodies [12]. Appoint early — a lead assessor must review the assessment before the director sign-off, so their availability sits on your critical path, not at the end of it.

The exemptions are precise: no lead assessor is needed where total consumption is below 40,000 kWh a year, where ISO 50001 covers total or significant consumption, or — new under regulation 33A — where consumption is zero [3].

Engaging wider support is a separate decision from the statutory sign-off: choosing an ESOS consultant covers what a compliant engagement has to produce and what to ask before appointing one.

ESOS is not SECR — check both, separately

The two regimes are deliberately distinct: ESOS is a four-yearly energy audit; SECR is an annual disclosure in the accounts [13].

Their scope tests do not even agree — and SI 2026/701 left that disagreement standing, deferring threshold alignment to Phase 5 [3].

A company can be in one, both, or neither — run each test independently, on the SECR reporting guide and this page.

The energy dataset, though, is one dataset: the kWh figures an ESOS audit produces are the backbone of SECR’s annual disclosure and of UK SRS S2 Scope 1 and 2 reporting — ESOS and UK SRS maps the reuse.

What Phase 5 already holds

Two decisions about the next cycle have already been taken, both by deferral.

Mandatory net zero reporting was proposed for Phase 4 and postponed to Phase 5 — voluntary alignment via PAS 51215 is available now for organisations that want to run ahead of the duty [11].

ESOS/SECR threshold alignment is likewise deferred — the two regimes keep their different tests for all of Phase 4 [3].

The power to make both changes already exists — the Energy Act strengthening powers were set out in the government’s own factsheet [16]. Phase 5 is a policy decision away, not a legislation programme away.

Doing it in-house, or not

Phase 4 splits cleanly into what only you can do, what a named professional must do, and what anyone competent can do.

Only you: confirming scope, board sign-off, and owning the action plan. A named professional: the lead assessor sign-off, from the six approved registers above. Anyone competent: data gathering, site work and submission mechanics — in-house or bought in.

If you outsource delivery, specialist ESOS consultants run the audits and notification end to end — and choosing a sustainability consultant covers how to test any firm before appointing it.

The software question is separate from the consultancy one: carbon reporting software compares the platforms that hold the kWh dataset between phases.