Yes, for large UK undertakings: 250 or more employees, or turnover over £44 million together with a balance sheet total over £38 million, including any UK group containing such an undertaking. Smaller organisations are outside the scheme and audit voluntarily.

When is the next ESOS deadline?

Phase 4 qualification is tested on 31 December 2026 and the compliance deadline is 5 December 2027. Phase 3's deadline (5 June 2024) has passed; late qualifiers should still notify rather than wait for Phase 4.

Guide

ESOS explained: who qualifies, deadlines and audit costs in 2026

Updated 2026-08-14

The Energy Savings Opportunity Scheme is the one energy audit that is not optional. If your organisation qualifies, the audit, the lead assessor sign-off and the notification all have to happen by the phase deadline.

What ESOS is

ESOS is a mandatory energy assessment scheme for large UK undertakings, administered by the Environment Agency. Every four years, qualifying organisations must measure their total energy consumption, audit at least 95% of it, have the work reviewed and signed off by a registered ESOS lead assessor and a board-level director, and notify the Environment Agency (gov.uk ESOS guidance).

Who qualifies

250 or more employees in the UK, or
Annual turnover over £44 million AND a balance sheet total over £38 million, or
Membership of a corporate group that contains a qualifying undertaking, the whole UK group is then in scope.
Qualification is tested on a snapshot date: 31 December 2026 for Phase 4. If you qualify on that date, you must comply even if headcount later falls.

The deadlines

Phase 3: Compliance deadline was 5 June 2024. If you qualified and have not notified, you are late, not exempt, speak to an assessor now.
Phase 4 qualification date: 31 December 2026. Check headcount and accounts against the thresholds on this date.
Phase 4 compliance deadline: 5 December 2027. Audits, lead assessor review, director sign-off and notification all complete by then.

What ESOS compliance costs

There is no standard tariff. The price depends on how many sites you have, how good your half-hourly and fleet data is, and whether you already hold ISO 50001 (which is itself a compliance route). Single-site qualifiers at the small end are typically quoted in the low thousands; multi-site portfolios cost more. Treat any figure you have not had quoted for your own estate as a guess, the ranges vary too much to publish a reliable number, so get quotes for your actual site list.

Routes to compliance

ESOS energy audits, the standard route: audits covering at least 95% of total energy consumption, overseen by a registered lead assessor.
ISO 50001, a certified energy management system covering your energy use can stand in for audits.
Display Energy Certificates and Green Deal Assessments can count towards compliance for the buildings they cover.
Whichever route, a board director must sign off and the notification must reach the Environment Agency by the deadline.

Non-compliance carries civil penalties which can reach £50,000, with further daily penalties for continued failure (see the enforcement section of the gov.uk ESOS guidance). The audit is nearly always cheaper than the fine.