ESOS Phase 4: dates, requirements and changes

The compliance date is 5 December 2027. By then a qualifying organisation must have completed its ESOS assessment, or used ISO 50001, had it reviewed by its responsible officer or officers, and submitted a notification of compliance to the Environment Agency through MESOS. The Phase 4 compliance period runs from 6 December 2023 to 5 December 2027.

31 December 2026. An undertaking qualifies if on that date it employs at least 250 persons, or has an annual turnover in excess of £44 million and an annual balance sheet total in excess of £38 million. Both money limbs must be exceeded, and a group in which any UK undertaking qualifies participates as a whole.

The action plan must be notified within the year starting 6 December 2027, so the last day is 5 December 2028. It covers the following compliance period, 6 December 2027 to 5 December 2031. Progress updates follow by 5 December 2029, 5 December 2030 and 5 December 2031.

The regulations call it a progress update: a written record, notified through MESOS, of which action-plan measures have been implemented, whether on time, which have not, and an estimate in kWh of the energy saving in the period with the method used. Phase 4 participants make three, the third added by SI 2026/701 regulation 28.

SI 2026/701, in force 22 July 2026, removed Display Energy Certificates and Green Deal Assessments as compliance routes; made ISO 50001 covering total or significant consumption discharge the lead assessor, audit and report duties; required the ESOS report to state the energy savings achieved and to review the previous action plan; added a third progress update; put estimates in kWh; widened the insolvency exclusion; and gave lead assessors a personal duty to notify their approval body. The qualification thresholds and the 95% coverage rule did not change.

Yes. An organisation may identify areas of significant energy consumption making up not less than 95% of its total, measured in energy units or by energy spend, and exclude the remaining 5% as de minimis. The figure rose from 90% to 95% under the 2023 amendment regulations, so it applied from Phase 3. It is a floor, and identifying significant consumption is optional: an organisation that does not do so must cover its total consumption.

The ESOS report records the outcome of the assessment: total and significant energy consumption, an energy intensity ratio for each organisational purpose, the energy audit findings and recommended measures, and, new in Phase 4, the energy savings achieved in the period and a review of any previous action plan identifying measures not implemented and why. It is shared with group undertakings and kept in the evidence pack; a notification of compliance is what is submitted.

Failing to undertake an assessment carries up to £50,000 plus up to £500 per working day for up to 80 working days; failing to notify carries up to £5,000 plus the same daily penalty; failing to keep records carries up to £5,000 plus audit costs; a false statement carries up to £50,000; and every penalty can be published. There is no penalty in the regulations for failing to submit an action plan or progress update; the failure is published instead.

Yes. Where ISO 50001 certification covers all of the participant’s total or significant energy consumption, it is deemed to have complied with the duties to appoint a lead assessor, carry out the audit and produce the ESOS report. The certificate must be issued after 5 December 2023 and valid on 5 December 2027. A notification of compliance is still required, and partial certification exempts only the certified part.

No. The Environment Agency’s Phase 4 guidance says participation in UK ETS, Climate Change Agreements, SECR and other schemes does not automatically count as ESOS compliance. Their data can help calculate total energy consumption, and a CCA energy audit may count if it was conducted, verified or reviewed by a lead assessor and meets the ESOS minimum standards.