ESOS Phase 4: The 31 December 2026 Qualification Date and the 2027 Deadline
In brief
- ESOS, the Energy Savings Opportunity Scheme, requires large UK organisations to audit their energy use and find ways to save energy every four years.
- Phase 4 is decided by your status on 31 December 2026. You qualify if, on that date, you are a large undertaking or part of a group with one.
- A large undertaking has 250 or more employees, or annual turnover above £44 million and a balance sheet above £38 million.
- The notification of compliance is due by 5 December 2027. An action plan follows by 5 December 2028, with yearly progress updates.
ESOS Phase 4 starts with a date that is only weeks away: 31 December 2026. Whether your organisation is in scope depends on its size on that day, and the compliance work then runs through 2027. Here is who qualifies, what you must do, and how it connects with SECR and a Carbon Reduction Plan.
Do you qualify for Phase 4?
| Test | Large undertaking if |
|---|---|
| Employees | 250 or more |
| Or money | Turnover above £44 million and balance sheet above £38 million |
| Groups | If one UK company in a group is large, the whole UK group must comply, normally as one participant |
The tests apply to individual undertakings, not to the group total, but one large undertaking brings in the whole UK group. Note that these tests differ from SECR’s two-of-three test (see SECR requirements), so a company can be in one scheme and not the other.
What you must do
| Step | Deadline |
|---|---|
| Measure total energy use (buildings, industrial processes, transport) for a 12-month reference period that includes 31 December 2026 | Before the audit |
| Energy audits, overseen by a registered lead assessor, to find cost-effective savings | During 2027 |
| Board-level sign-off and notification of compliance to the Environment Agency | 5 December 2027 |
| Action plan setting out the savings measures you will take | 5 December 2028 |
| Annual progress updates on the action plan | 2029, 2030 and 2031 |
Organisations with an ISO 50001 energy management system covering all their energy use can use it as a route to compliance instead of separate audits.
What happens if you miss it?
Missing the compliance notification can lead to enforcement and civil penalties. Missing the action plan or progress updates does not bring a penalty, but the Environment Agency publishes which organisations failed to submit them. Note also that the government has moved deadlines before: the Phase 3 date was delayed. Plan for 5 December 2027 and watch for changes.
Use the work twice
An ESOS audit measures the same energy as SECR and the Scope 1 and 2 parts of a Carbon Reduction Plan. If you collect the data once, for the same 12 months, you can use it for all three. The savings measures in the action plan can also become the reduction measures in your Carbon Reduction Plan, which customers and public buyers read.
ESOS is the only one of these schemes that asks where you could save money. Treat it as an energy review, not a form.
Our GHG accounting service prepares the energy and emissions data. The audits themselves must be overseen by a registered ESOS lead assessor.
Frequently asked questions
What is the ESOS Phase 4 qualification date?
31 December 2026. You qualify if your organisation meets the large undertaking test on that date.
When is the ESOS Phase 4 deadline?
The notification of compliance is due by 5 December 2027. The action plan is due by 5 December 2028.
Who must comply with ESOS?
Large UK undertakings, with 250 or more employees or turnover above £44 million and a balance sheet above £38 million, and the UK companies in their groups.
Is ESOS the same as SECR?
No. ESOS is an energy audit every four years; SECR is yearly reporting in the annual report. The size tests are also different.
Do I need a lead assessor?
Yes. ESOS audits must be carried out or reviewed by a registered lead assessor, unless you comply through ISO 50001.
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