ESOS Phase 4: deadlines, qualification and how to comply

What ESOS Phase 4 is

The Energy Savings Opportunity Scheme (ESOS) runs in four-year compliance phases. Phase 3 closed with the extended notification deadline in 2024; Phase 4 is the live cycle, with a qualification date of 31 December 2026 and a compliance deadline of 5 December 2027.

In each phase, qualifying organisations must measure their total energy consumption, audit at least 95% of it, identify cost-effective energy-saving opportunities, and notify the scheme regulator — the Environment Agency in England, with SEPA, NRW and NIEA covering the devolved nations.

Who qualifies for Phase 4

You are in scope if, on 31 December 2026, your UK organisation meets either test:

Corporate groups qualify together: if any UK undertaking in your group meets a test, the whole UK group participates, normally under one lead responsible undertaking. Note the ESOS thresholds are different from the SECR thresholds — many organisations are caught by both regimes, but each test stands alone.

Key Phase 4 dates

What changed after Phase 3

Phase 3 tightened the scheme, and those changes carry into Phase 4:

• Action plans — after notifying, organisations must publish an action plan setting out which energy-saving measures they will implement, and report progress against it through annual progress updates.
• 95% coverage — de minimis exclusions are limited to 5% of total energy consumption (down from 10% in earlier phases).
• Standardised reporting — more energy and intensity detail is reported through the online notification system, making year-on-year performance visible.

Your compliance routes

Most organisations comply through an ESOS energy audit signed off by a registered ESOS Lead Assessor. Alternative routes can cover some or all of your energy use:

• ISO 50001 — a certified energy management system covering your total energy consumption removes the need for a separate ESOS audit.
• Display Energy Certificates and Green Deal Assessments — can count towards compliance for the buildings they cover.

Whatever the route, a board-level director must review and sign off the assessment before notification.

ESOS and SECR: don't run them separately

The energy data underneath an ESOS assessment is largely the same data your SECR disclosure reports every year. Collecting it once, to an audit-ready standard, serves both regimes — and the energy-saving opportunities your assessor identifies become the energy-efficiency narrative in your Directors' Report. See our full SECR vs ESOS comparison.

How to prepare now

1. Check qualification early — measure your headcount and financials against the tests well before 31 December 2026, including every UK group entity.
2. Start collecting energy data — the measurement period must include the qualification date, so 2026 consumption data (electricity, gas, transport fuel) is what you will audit.
3. Book an assessor before the rush — registered ESOS Lead Assessors are a finite pool, and every qualifying organisation in the UK shares the same 5 December 2027 deadline. Phase 3 ended in a scramble; Phase 4 will too.
4. Close out Phase 3 obligations — if you notified in Phase 3, keep your action plan progress updates current; the regulator can issue penalties for missed updates.

Non-compliance carries civil penalties — an initial fine plus daily penalties while the breach continues, and publication of your organisation's failure.

Want it handled? A vetted, registered ESOS Lead Assessor can scope your Phase 4 obligation, run the audit and file the notification — speak to a specialist, free and no obligation.