ESOS Deadlines
ESOS Deadlines: All Key Dates for Phase 3 and Phase 4 (2026)
Phase 3 Progress Update 2 is due 5 December 2026.
Phase 4 qualification falls on 31 December 2026, with the Phase 4 compliance notification due 5 December 2027.
This tracker covers every active ESOS deadline and the consequences of missing them.
ESOS Deadlines Overview
1 The Energy Savings Opportunity Scheme runs in four-year compliance phases administered by the Environment Agency, with each phase comprising a qualification date, a compliance period, a notification deadline and a series of follow-on action plan and progress reporting obligations.
Two phases are currently live in 2026: Phase 3 remains active for progress reporting against action plan commitments, and Phase 4 is in its preparation window ahead of the 31 December 2026 qualification date.
Organisations in scope of ESOS requirements must track multiple overlapping deadlines, with the next major date for Phase 3 participants being 5 December 2026 for Progress Update 2.
Phase 4 deadlines
3 ESOS Phase 4 runs on the standard four-year compliance cycle. The qualification date of 31 December 2026 determines which UK organisations are in scope, and the compliance notification must be submitted by 5 December 2027.
The four-year compliance period began on 6 December 2023, giving organisations a full audit window from which to draw 12 months of verifiable energy consumption data. Phase 4 also removes Display Energy Certificates and Green Deal Assessments as standalone compliance routes, requiring energy audits or ISO 50001 certification as the primary pathway covered in our energy audit guide.
Qualification Date — 31 December 2026
Organisations are assessed against ESOS qualification criteria on this date. Any UK group with 250+ employees, or turnover above £44m and balance sheet above £38m, is in scope for Phase 4 regardless of size on later dates.
Compliance Period — 6 December 2023 to 5 December 2027
Four-year window during which Phase 4 audit data must be drawn. Audit periods must cover 12 months of energy use within the 24 months ending on the compliance deadline.
Notification Deadline — 5 December 2027
Final date for submitting Phase 4 compliance notification via the Manage your ESOS (MESOS) portal. Submission must include energy audit findings, intensity ratios, identified savings opportunities and board-level director sign-off.
Action Plan Submission — within Phase 4 cycle
Phase 4 introduces progress reporting against Phase 3 action plan commitments as part of the assessment. Where commitments have not been met, organisations must provide an explanation in the Phase 4 submission.
Phase 4 Notification Deadline
Final date for submitting Phase 4 compliance notification via MESOS, with board-level director sign-off, completed energy audit and action plan progress reporting
Working backwards from 5 December 2027
Most organisations need to begin scoping by mid-2026 to allow time for lead assessor appointment, energy data collection, site visits and board sign-off.
A realistic countdown from the notification date is: 18 months out for assessor appointment and data scoping, 12 months out for audit execution, 6 months out for draft report and 3 months out for board review and MESOS submission.
Phase 3 deadlines
4 Phase 3 obligations did not end with the 5 June 2024 notification deadline. The 2023 Amendment Regulations introduced action plans and annual progress updates that continue throughout the Phase 4 compliance period, meaning Phase 3 participants remain actively in scope through 5 December 2026 and beyond.
Phase 3 also introduced enhanced coverage requirements (95% of total energy consumption, up from 90%) and mandatory site visits — see our breakdown of ESOS reporting requirements for the technical detail.
Original Compliance Date — 5 December 2023
Statutory Phase 3 compliance notification deadline under SI 2014/1643 as amended. Most organisations were not able to meet this date due to delayed launch of the MESOS portal.
Extended Compliance Date — 5 June 2024
Environment Agency extended the Phase 3 notification deadline by six months to allow time for portal launch and updated guidance. Further enforcement grace period was applied until 6 August 2024.
Action Plan Deadline — 5 December 2024 (extended to 5 March 2025)
Primary deadline for submitting the Phase 3 action plan was 5 December 2024. Environment Agency accepted late submissions without remedial action until 5 March 2025. Late submission after this date now risks enforcement.
Progress Update 1 — 5 December 2025
First annual progress update against action plan commitments. Covers the 12-month reporting period 6 December 2024 to 5 December 2025. Board-level sign-off required.
Progress Update 2 — 5 December 2026
Second annual progress update covering 6 December 2025 to 5 December 2026. This is the next major ESOS deadline for Phase 3 participants and requires reporting on implemented energy reduction measures.
Action plan deadlines
6 Action plans were introduced by the 2023 Amendment Regulations as a forward-looking commitment document listing energy-saving measures, projected savings and implementation timelines. Submission is a legal requirement, not optional, and the Environment Agency has powers to compel filing where organisations fail to comply.
The full action plan lifecycle spans from the original 5 December 2024 submission deadline through to Phase 4 carry-forward in December 2027:
Step 1 — Compliance notification first
Action plans cannot be submitted on MESOS until the Phase 3 compliance notification has been filed. Late notification participants must clear that filing before action plan or progress reports become available.
Step 2 — Submit action plan
Phase 3 action plan deadline was 5 December 2024 (extended to 5 March 2025). Plan must list energy-saving measures, projected savings and implementation timelines. Director sign-off mandatory.
Step 3 — Annual progress updates
Two annual updates due 12 months and 24 months after the action plan deadline. For Phase 3 these are 5 December 2025 and 5 December 2026. Each covers the preceding 12 months of implemented actions.
Step 4 — Phase 4 carry-forward
Progress against Phase 3 action plan commitments must be included in the Phase 4 assessment submitted by 5 December 2027. Unmet commitments require written explanation in the Phase 4 notification.
Sequencing constraint
Action plans cannot be submitted on the MESOS system until the Phase 3 compliance notification has been filed. Organisations that are still late on Phase 3 notification need to clear that filing first before action plan or progress report submissions become technically possible.
Detailed guidance on plan content and director sign-off is covered in our ESOS action plan guide.
Annual progress update deadlines
Following the action plan submission, Phase 3 participants must file two annual progress updates covering implemented energy-saving measures and actual outcomes. Each update covers the preceding 12 months and requires board-level director sign-off.
Phase 3 progress update deadlines:
• 5 December 2025 — Progress Update 1, covering 6 December 2024 to 5 December 2025
• 5 December 2026 — Progress Update 2, covering 6 December 2025 to 5 December 2026
Progress updates do not strictly require lead assessor sign-off, but many organisations involve their assessor where implemented actions go beyond the original ESOS recommendations to ensure accurate quantification of savings.
Phase 3 Progress Update 2
Next major ESOS deadline.
Covers implemented energy-saving measures from 6 December 2025 to 5 December 2026 against the Phase 3 action plan commitments
Public disclosure
7 The Environment Agency publishes all action plans and progress updates. Where no plan or update has been submitted, this absence is itself visible on the public register, signalling non-compliance to customers, investors and procurement teams. This public-disclosure dimension is particularly relevant for organisations also subject to UK SRS sustainability reporting.
What happens if you miss a deadline
8 The Environment Agency is responsible for ESOS enforcement in England, with equivalent administrators in Scotland, Wales and Northern Ireland. Civil penalties under Regulations 43 to 49 of SI 2014/1643 apply where organisations fail to meet their obligations.
The enforcement process typically follows a four-step approach: compliance notice, enforcement notice, civil penalty notice and publication penalty. Penalties scale with the seriousness of the breach and any history of prior non-compliance.
Failure to notify — up to £45,000
Regulation 43 sets an initial penalty of up to £5,000, plus a daily penalty of up to £500 for each working day in breach (capped at 80 working days = £40,000), plus a publication penalty naming the organisation.
Failure to undertake energy audit — up to £90,000
Regulation 45 sets the most serious financial penalty: initial penalty up to £50,000, daily penalty up to £500 per working day up to 80 days (£40,000), publication penalty, plus remedial action requirements.
Failure to maintain records — up to £5,000
Maximum penalty of £5,000 plus publication for failure to keep evidence packs supporting the ESOS assessment for the required retention period.
Failure to comply with a notice — up to £45,000
Penalty applies when organisations fail to provide information or take steps required by a compliance, enforcement or penalty notice issued by the Environment Agency.
Mitigation if you have already missed a deadline
Immediate steps include appointing a qualified lead assessor, contacting the Environment Agency to demonstrate intent, and completing the outstanding audit and notification as soon as possible. Regulators have powers to waive or modify penalties for organisations showing genuine remedial action.
Penalties escalate quickly once a compliance notice is served — the daily penalty clock starts the working day after service and runs for up to 80 working days.
Reminders and best practice
ESOS deadlines are now sufficiently overlapping that ad-hoc tracking is unreliable. Organisations that treat Phase 4 preparation as a 2027 problem typically encounter audit capacity constraints, board sign-off bottlenecks and incomplete energy data in the final six months.
The most resilient approach is to maintain a single deadline calendar integrating Phase 3 progress updates, Phase 4 qualification and notification, and overlapping UK SRS timeline dates where relevant.
Diarise 18 months ahead
Phase 4 notification (5 December 2027) requires a lead assessor appointment, 12 months of energy data and site visits. Most organisations need to start scoping work by mid-2026 to avoid rushed audits.
Track Phase 3 progress quarterly
Progress Update 2 (5 December 2026) requires quantified outcomes from implemented measures. Quarterly tracking of action plan items reduces year-end reconstruction effort and supports accurate reporting.
Confirm group structure before qualification date
Companies acquired before 31 December 2026 count toward Phase 4 qualification. Companies sold before that date are excluded. Plan structural changes with awareness of the qualification date.
Maintain a single evidence repository
Retain audit data, lead assessor certifications, board sign-off documentation and progress reports for at least two compliance periods. Central storage supports both ESOS and overlapping SECR and UK SRS reporting.
Integrating with wider reporting
ESOS audit data feeds directly into SECR streamlined energy and carbon reporting and increasingly into UK SRS sustainability disclosures. Organisations that align ESOS, SECR and UK SRS reporting cycles reduce duplication and improve data consistency across all three regimes.
See our ESOS and UK SRS integration guide for how the 5 December 2027 Phase 4 deadline aligns with the wider 2026-2027 sustainability reporting calendar.
What is the next ESOS deadline I need to meet?
For Phase 3 participants, the next major deadline is 5 December 2026 for Progress Update 2 covering the period 6 December 2025 to 5 December 2026.
For all qualifying organisations, the Phase 4 qualification date is 31 December 2026, followed by the Phase 4 notification deadline on 5 December 2027.
When is the ESOS Phase 4 deadline?
ESOS Phase 4 has two key deadlines: 31 December 2026 is the qualification date used to determine which organisations are in scope, and 5 December 2027 is the compliance notification deadline by which audits must be completed and submitted via the MESOS portal with board-level director sign-off.
When was the ESOS action plan deadline?
The Phase 3 action plan deadline was 5 December 2024, extended by the Environment Agency to 5 March 2025 due to delays in the MESOS portal.
Phase 4 will introduce a new action plan cycle following the 5 December 2027 notification, with two further annual progress updates required.
What happens if I miss an ESOS deadline?
The Environment Agency can issue compliance, enforcement and civil penalty notices.
Maximum penalties are £50,000 initial plus £40,000 in daily penalties for failure to undertake an energy audit, and £5,000 plus £40,000 daily for failure to notify.
Breaches are also published on a public register.
Are there penalties for late ESOS action plans or progress updates?
There is no direct financial penalty schedule for late action plans or progress updates, but failure to submit places the organisation on a public register showing no energy efficiency actions are being taken.
The Environment Agency can use its enforcement powers to compel submission, and ongoing non-compliance escalates to civil penalties.
Do Phase 3 progress updates need lead assessor sign-off?
A lead assessor is not strictly required for Phase 3 progress updates, but board-level director sign-off is mandatory.
Many organisations choose to involve their lead assessor where implemented actions go beyond the original ESOS recommendations to ensure accurate reporting.
Related guides & references
What Is the ESOS Scheme?
Complete introduction to Energy Savings Opportunity Scheme framework
ESOS Phase 4: Deadline and Requirements
Phase 4 specific guidance covering qualification and compliance deadlines
ESOS Phase 3: Status and Late Compliance
Phase 3 compliance position, action plans and ongoing progress reporting
ESOS Action Plan Requirements
What to include in your action plan and progress updates
ESOS Requirements: The 7 Compliance Steps
Full compliance pathway from energy data through MESOS submission