Insights / ESOS Phase 4

ESOS Phase 4

ESOS Phase 4: the countdown.

13 November 2026 · 4 min read

ESOS is the government’s mandatory energy assessment scheme for large UK organisations. Phase 4 is the next four-year cycle, and the clock that matters most is already running: whether you are in or out is decided by your size on 31 December 2026.

Who is in

Your organisation is in Phase 4 if, on 31 December 2026, any UK company in your group is a large undertaking. That means it either:

• employs 250 or more people (employees, owners, managers and partners, full or part time), or
• has annual turnover over £44 million and a balance sheet total over £38 million. Both financial tests must be met together.

If one UK company in the group qualifies, the whole UK group is in. UK establishments of overseas companies can be caught too, whatever their own size, if the rest of the group’s UK activities meet the tests.

Not sure? Our 30-second ESOS check gives you a quick answer.

The dates, in order

1. 31 December 2026 — qualification date. Your size on this day decides whether you are in Phase 4.
2. 5 December 2027 — notification of compliance. Your energy audit must be complete, signed off by a lead assessor where required, and notified to the Environment Agency.
3. 5 December 2028 — action plan. The energy-saving measures you commit to, with targets.
4. 5 December 2029, 2030 and 2031 — progress updates. Three annual updates on that action plan. The third is new for Phase 4.

What has changed since Phase 3

• Display Energy Certificates and Green Deal assessments can no longer be used as a route to compliance.
• ISO 50001 certificates must have been issued after 5 December 2023 and still be valid on 5 December 2027.
• Your audit data must cover a 12-month period that starts no earlier than 6 December 2022.
• Action plan progress has to be reported, including an explanation for any commitments you didn’t meet.

What to do now

1. Confirm whether you qualify. Check headcount and accounts for every UK company in the group.
2. Pull together 12 months of energy data. Buildings, industrial processes and transport, including fuel for your fleet.
3. Book your audit early. Lead-assessor capacity tightens as December 2027 approaches, and audits that start late tend to rely on estimates rather than measured data.
4. Think beyond the audit. The action plan and three progress updates mean ESOS now runs to 2031. Measured data, such as an Energy Fingerprint, makes those updates far easier to evidence.

How we help

We deliver the full Phase 4 package: qualification check, audit, lead-assessor sign-off, notification, and tracking of your action plan through the progress updates in the Identic EMS. You get a fixed quote within 48 hours. More on our ESOS service.

Sources: GOV.UK: Energy Savings Opportunity Scheme (ESOS). Correct at the date shown; rules can change, so check the source or ask us before acting.