ESOS Phase 3
ESOS Phase 3: Deadlines, Changes and Compliance
Complete guide to ESOS Phase 3 covering the 31 December 2022 qualification date, extended 5 June 2024 deadline, mandatory action plans and the 95% coverage threshold introduced by the Amendment Regulations 2023.
ESOS Phase 3 Overview
1 ESOS Phase 3 was the third four-year compliance cycle of the Energy Savings Opportunity Scheme, running from 6 December 2019 to 5 December 2023 with qualification assessed on 31 December 2022.
Phase 3 marked the most significant evolution of the scheme since its 2014 introduction, with 2 the ESOS (Amendment) Regulations 2023 introducing new action plan obligations, annual progress updates, increased energy coverage and public disclosure of compliance data.
The compliance deadline was extended from 5 December 2023 to 5 June 2024 to give participants time to meet the new requirements, with a further late submission window to 6 August 2024 due to delays launching the Manage your ESOS (MESOS) online portal. For the current cycle, see our ESOS Phase 4 compliance guide.
Phase 3 Timeline and Key Deadlines
3 Phase 3 spans an eight-year window from the start of the compliance period to the final progress update, with multiple statutory deadlines under the Energy Savings Opportunity Scheme Regulations 2014 as amended.
Each deadline triggers a specific submission obligation through the MESOS system, with board-level director sign-off required at every stage. Missing a deadline exposes the organisation to enforcement action from the Environment Agency.
The timeline below reflects all confirmed Phase 3 statutory dates, including the extensions granted under the Amendment Regulations 2023 and Environment Agency operational deadlines.
6 December 2019 - Phase 3 begins
ESOS Phase 3 compliance period started, running for four years until 5 December 2023, with 12 months of verifiable energy data required from this date onwards
31 December 2022 - Qualification date
Snapshot date used to determine which organisations qualified as large undertakings for Phase 3 obligations, with status assessed on this single date
5 December 2023 - Original deadline
Statutory compliance notification deadline under the original ESOS Regulations 2014, before the Amendment Regulations 2023 extended the date
5 June 2024 - Extended deadline
Final extended deadline for submitting Phase 3 compliance notifications, granted to give organisations time to meet new Amendment Regulations 2023 requirements
6 August 2024 - Late submission window
Environment Agency confirmed acceptance of late notifications until 6 August 2024 due to delays launching the MESOS online compliance portal
5 December 2024 - Action plan deadline
New mandatory deadline introduced by Phase 3 for submission of forward-looking action plans, with late submissions accepted until 5 March 2025
5 December 2025 - First progress update
First annual progress update against the Phase 3 action plan, reporting on energy efficiency measures implemented in the previous 12 months
5 December 2026 - Second progress update
Second and final annual progress update covering Phase 3 commitments, due before transition into Phase 4 compliance reporting
Phase 3 Extended Deadline
Final statutory deadline for ESOS Phase 3 compliance notification, extended from the original 5 December 2023 date by the Amendment Regulations 2023
Who Qualified for ESOS Phase 3
4 Phase 3 applied to any UK organisation or corporate group containing a UK entity that met the large undertaking criteria on the 31 December 2022 qualification date.
An organisation qualified for Phase 3 if on 31 December 2022 it:
- Employed 250 or more people in the UK, OR
- Had an annual turnover above £44 million AND a balance sheet total above £38 million
Qualification was assessed across the entire UK corporate group. If any single entity in the group met the threshold, the entire UK group was within scope. Organisations qualified for ESOS retain their status until failing the test for two consecutive accounting periods.
Do Not Qualify notifications
Organisations that previously qualified for Phase 2 but did not meet the Phase 3 criteria on 31 December 2022 were encouraged to submit a Do Not Qualify (DNQ) notification to the Environment Agency.
DNQ notifications confirm the organisation's status and remove it from active compliance monitoring, avoiding unnecessary enforcement queries. The full exemptions framework details all qualification edge cases.
What Changed in Phase 3
5 The ESOS Amendment Regulations 2023 (SI 2023/1182) came into force on 29 November 2023 and applied retrospectively to Phase 3, fundamentally reshaping the compliance framework.
The changes were designed to drive greater action on energy efficiency, improve audit quality, and align the scheme with the UK's net zero commitments and the broader UK SRS sustainability reporting framework.
Seven major changes apply to Phase 3 participants. These changes carry forward into Phase 4 and form the basis of ongoing ESOS evolution under the 6 Environment Agency.
Coverage increased from 90% to 95%
The de minimis exemption was reduced from 10% to 5%, requiring significant energy consumption to cover at least 95% of total energy use across buildings, processes and transport
Mandatory action plans introduced
All Phase 3 participants must submit a forward-looking action plan within 12 months of the compliance deadline, detailing energy saving measures and expected kWh savings
Annual progress updates required
Organisations must submit two annual progress updates after the action plan, reporting against committed measures in December 2025 and December 2026
Energy intensity ratios required
ESOS reports must now include energy intensity metrics in kWh by organisational purpose, enabling comparisons across phases and alignment with SECR reporting
Public disclosure of compliance data
Environment Agency publishes most compliance data including total energy consumption, intensity ratios, action plans and annual progress reports openly
Enhanced ESOS report content
Reports must include compliance summary template, details on next steps for implementation, and more specific cost-benefit analysis of energy saving opportunities
Mandatory corporate group sharing
ESOS report details must be shared with all members of the corporate group to ensure consistent awareness of energy efficiency opportunities across the organisation
Phase 3 vs Phase 2 Comparison
Phase 3 represented a significant tightening of obligations compared to Phase 2 (which ran 6 December 2015 to 5 December 2019). While the qualification thresholds remained the same, the substantive compliance requirements expanded considerably.
Energy coverage: Phase 2 required audits covering 90% of total energy consumption with a 10% de minimis exemption. Phase 3 increased this to 95% with a 5% de minimis.
Action plans: Phase 2 had no action plan requirement. Phase 3 introduced a mandatory forward-looking action plan due within 12 months of the compliance deadline.
Progress updates: Phase 2 ended with a single compliance notification. Phase 3 added two annual progress updates against the action plan in the following years.
Energy intensity ratios: Phase 2 did not require intensity metrics. Phase 3 mandated energy intensity ratios in kWh per organisational purpose, similar to the metrics used in SECR reporting.
Public disclosure: Phase 2 information was largely private to the regulator. Phase 3 introduced public disclosure of most compliance data including the action plan and progress updates on the Environment Agency portal.
Lead assessor scope: Phase 2 required lead assessor sign-off for most audits. Phase 3 extended this with stricter quality standards and more rigorous methodology requirements, building on qualified lead assessor oversight.
Phase 3 to Phase 4 Transition
7 Phase 4 began on 6 December 2023, immediately following the end of the Phase 3 compliance period. The two phases therefore overlap, with Phase 3 progress reporting continuing through 2026 while Phase 4 preparation runs in parallel.
What carries forward from Phase 3:
- 95% energy coverage threshold (now baseline)
- Mandatory action plans and annual progress updates
- Energy intensity ratio reporting
- Public disclosure of compliance data
- Lead assessor approval for all audit work
- Board-level director sign-off requirements
What is new in Phase 4:
- Display Energy Certificates (DECs) removed as compliance route
- Green Deal Assessments (GDAs) removed as compliance route
- Stricter audit quality standards under BS EN 16247
- Phase 3 progress updates feed into Phase 4 baseline data
Organisations that qualified for Phase 3 must continue Phase 3 progress reporting while preparing for the Phase 4 qualification date of 31 December 2026. For full Phase 4 guidance, see our dedicated compliance guide. The connection between ESOS energy data and broader emissions reporting is explored in our SECR reporting guide.
Phase 3 Enforcement and Penalties
8 The Environment Agency is responsible for ESOS enforcement in England and acts as the lead administrator for the scheme across the UK. Civil sanctions may be imposed under the Environment Agency's enforcement and sanctions policy.
Civil penalties available for Phase 3 breaches:
- Failure to notify compliance: up to £50,000 plus £500 per day of continued non-compliance
- Failure to maintain an evidence pack: up to £5,000
- Failure to undertake an energy audit: up to £50,000 plus £500 per day
- False or misleading statements: up to £50,000
- Failure to submit an action plan: up to £5,000 plus £500 per day
Organisations that qualified for Phase 3 but failed to submit a notification of compliance by 6 August 2024 are now at active risk of enforcement action and should contact the Environment Agency immediately to mitigate sanctions. A summary of penalties imposed is published openly on data.gov.uk.
Publication of compliance data
9 One of the most significant Phase 3 changes is the public disclosure of compliance information. The Environment Agency publishes most data from the notification of compliance, action plan and progress updates.
Published information includes total and significant energy consumption, energy intensity ratios, estimated potential energy reduction, energy savings achieved since the previous compliance period, the action plan content and annual progress reports.
Personal data and genuinely commercially sensitive information can be redacted, but the default position is public transparency. This represents a major shift in regulatory approach designed to encourage meaningful action on energy efficiency, mirroring the disclosure principles in UK SRS sustainability reporting.
When was the ESOS Phase 3 compliance deadline?
The original ESOS Phase 3 compliance deadline was 5 December 2023.
This was extended to 5 June 2024 through the ESOS Amendment Regulations 2023 to give participants time to meet enhanced requirements.
The Environment Agency then accepted late submissions until 6 August 2024 due to delays launching the MESOS online portal.
The action plan deadline that followed was 5 December 2024, with late submissions accepted until 5 March 2025.
What was the qualification date for ESOS Phase 3?
The qualification date for ESOS Phase 3 was 31 December 2022.
Organisations that met the large undertaking criteria on this single snapshot date were required to comply with Phase 3, even if they no longer met the criteria afterwards.
Qualification was based on either employing 250 or more people in the UK, or having an annual turnover above £44 million AND a balance sheet total above £38 million.
What changed between ESOS Phase 2 and Phase 3?
Phase 3 introduced significant changes through the ESOS Amendment Regulations 2023 (SI 2023/1182).
Coverage increased from 90% to 95% of total energy consumption, mandatory action plans were introduced for the first time, annual progress updates became required, energy intensity ratios had to be reported, and most compliance data became publicly disclosed.
ESOS reports also required more detail on implementation pathways and corporate group information sharing.
What is the ESOS Phase 3 action plan deadline?
The Phase 3 action plan submission deadline was 5 December 2024, exactly 12 months after the original Phase 3 compliance deadline.
The Environment Agency confirmed that late submissions would be accepted until 5 March 2025 without remedial action consideration.
The action plan must be signed off by a board-level director and submitted through the MESOS system.
What happens if my organisation missed the Phase 3 deadline?
Organisations that qualified for Phase 3 but failed to submit a compliance notification are at immediate risk of Environment Agency enforcement action.
Civil sanctions may include financial penalties of up to £50,000 plus £500 per day for continued non-compliance.
The Environment Agency has actively contacted non-compliant organisations and is publishing details of penalties imposed on data.gov.uk.
Do Phase 3 obligations carry forward into Phase 4?
Yes.
Phase 3 participants must complete two annual progress updates due 5 December 2025 and 5 December 2026, even as Phase 4 begins.
The 95% coverage threshold, lead assessor requirements, action plan format and progress reporting structure all carry forward into Phase 4.
Phase 4 then removes Display Energy Certificates and Green Deal Assessments as compliance routes, tightening the framework further.
Related guides & references
ESOS Phase 4 Compliance Guide
Current phase requirements with 5 December 2027 deadline and tightened compliance routes
What Is the ESOS Scheme?
Complete introduction to the Energy Savings Opportunity Scheme four-phase framework
ESOS Action Plan Requirements
How to prepare action plans and annual progress updates introduced in Phase 3
ESOS Energy Audit Guide
Methodology, site visit obligations and 12-month data requirements for ESOS audits
ESOS Requirements: 7 Compliance Steps
Step-by-step compliance pathway covering audits, assessors and submission