Sustainability reporting frameworks explained (CSRD, ISSB, TCFD, SECR, ESOS)

ESOS and SECR are two UK schemes that push large organizations to measure and report their energy use and carbon emissions. CSRD, ISSB and TCFD are wider sustainability reporting frameworks. This guide gives a plain definition of ESOS and SECR first and then the practical detail. It ends with a short guide to the other three frameworks.

What is ESOS?

ESOS is the Energy Savings Opportunity Scheme, a UK scheme that requires large organizations to carry out regular energy audits and identify ways to save energy. It was introduced under the Energy Savings Opportunity Scheme Regulations 2014 to meet the energy audit requirement of the EU Energy Efficiency Directive. The scheme runs in four-year compliance phases and the Environment Agency administers it for Great Britain.

Who ESOS applies to

ESOS applies to large undertakings and to corporate groups that include a large undertaking. An organization is generally in scope if, on the qualifying date, it meets either of these tests:

• It employs 250 or more people
• It has an annual turnover above about 50 million euros and an annual balance sheet total above about 43 million euros

Groups are assessed as a whole, so a parent company may need to include subsidiaries. Check the official guidance for current thresholds and for how to treat group structures.

What ESOS requires

Requirement	What it means
Assess whether you are in scope	Check the tests at the qualifying date for each phase
Measure total energy consumption	Cover buildings, industrial processes and transport
Carry out energy audits	Audit areas that account for at least 90% of total energy consumption
Use a lead assessor	A registered ESOS lead assessor must review the work and sign it off
Identify energy saving opportunities	Record recommendations with the expected savings
Get board-level sign-off	A director must approve the compliance
Notify the Environment Agency	Submit the compliance notification by the phase deadline
Keep evidence	Retain records for the period set out in the regulations

ESOS phases and timing

Each phase has a qualifying date and a compliance deadline. Phase 3 had a compliance deadline of December 5, 2023. Phase 4 has a qualifying date of December 31, 2026 and a compliance deadline of December 5, 2027. Phase 4 includes changes to the rules, so check the latest government guidance for what has changed.

How to prepare for ESOS

• Work out which entities fall in scope as soon as the qualifying date passes
• Collect energy data for buildings, processes and transport for a twelve-month reference period
• Appoint a lead assessor early, because capacity can be tight near the deadline
• Agree who signs off at board level
• Plan how recommendations will be assessed and acted on
• Keep a single evidence file with data, calculations, audit reports and sign-offs

An ESOS audit finds opportunities. It does not require you to carry out the recommended measures, but many organizations track them to deliver real savings.

What is SECR?

SECR is Streamlined Energy and Carbon Reporting, a UK requirement for certain companies to report their energy use and greenhouse gas emissions in their annual reports. It came into force for financial years starting on or after April 1, 2019, through the Companies (Directors' Report) and Limited Liability Partnerships (Energy and Carbon Report) Regulations 2018.

Who SECR applies to

• Quoted companies, which report on energy and carbon on a global basis
• Large unquoted companies and large limited liability partnerships (LLPs), which report on UK energy use and emissions

An unquoted company or LLP is generally large if it meets at least two of three tests on size: number of employees, turnover and balance sheet total. The thresholds were raised for financial years starting on or after April 6, 2025, so check the current figures.

What SECR requires you to report

Item	What to report
Energy use	Annual energy consumption, in kilowatt hours, from electricity, gas and transport fuel
Greenhouse gas emissions	Emissions in metric tons of carbon dioxide equivalent for scope 1 and scope 2, with some scope 3 sources such as business travel in private vehicles
Intensity ratio	At least one ratio, such as emissions per unit of output or per employee
Methodology	The method used to calculate the figures
Energy efficiency actions	Measures taken in the year to improve energy efficiency
Prior year comparison	Figures for the previous year

Quoted companies report global figures. Large unquoted companies and LLPs report UK figures. Where a company is below an energy use threshold, it can state that fact instead of giving the full detail. Check the regulations and government guidance for the exact rules.

ESOS vs SECR

Item	ESOS	SECR
Purpose	Find energy saving opportunities through audits	Report energy use and emissions publicly
Where it sits	A compliance notification to the Environment Agency	The directors' report in the annual accounts
Cycle	Every four years	Every financial year
Main output	Audit findings and recommendations	Energy, emissions and intensity figures
Covers	Energy use, including transport and industrial processes	Energy use and emissions, with different scope for quoted and unquoted companies

The two schemes overlap in their data. Energy and transport data collected for SECR each year can feed the ESOS audit every four years, so one clean data set saves work.

How to manage SECR reporting

• Set the reporting boundary to match the financial statements
• Collect energy and fuel data on a schedule through the year, not at year end
• Use recognized emission factors and note them in the methodology
• Pick an intensity ratio that is meaningful for the business
• Have finance and sustainability teams review the numbers together before the directors' report is finalized
• Keep the workings so the figures can be checked

SECR text sits inside the annual report, next to other narrative and financial disclosures. Finance teams working through annual report requirements can use checklists to make sure each obligation is covered. Ideagen Disclose is a disclosure management solution with checklists for financial reporting standards and ESG frameworks including ISSB, ESRS, TCFD and TNFD, so teams can check sustainability disclosures alongside the accounts. The people preparing the report still own the numbers and the final judgment.

How CSRD, ISSB and TCFD fit in

ESOS and SECR are UK energy and carbon requirements. CSRD, ISSB and TCFD are broader frameworks for sustainability and climate disclosure.

Framework	What it is	Where it applies
CSRD	The EU Corporate Sustainability Reporting Directive. It requires in-scope companies to report on sustainability matters using the European Sustainability Reporting Standards (ESRS), including impacts on people and the environment as well as financial risks and opportunities	EU, with some non-EU groups in scope. Scope and timing have been under review, so check the current position
ISSB	The International Sustainability Standards Board. It issued IFRS S1 on general sustainability disclosures and IFRS S2 on climate disclosures in June 2023, focusing on information useful to investors	Global baseline that jurisdictions can adopt. The UK is developing UK Sustainability Reporting Standards based on ISSB
TCFD	The Task Force on Climate-related Financial Disclosures. Its 2017 recommendations cover governance, strategy, risk management and metrics and targets	Widely used, with many national rules built on it. The task force was disbanded in 2023 and ISSB took over monitoring

What is CSRD?

CSRD is the EU law that sets sustainability reporting requirements for large and listed companies. It uses double materiality, which means companies report both how sustainability issues affect the business and how the business affects people and the environment. The rules and timelines have been under revision, so check current EU guidance.

What is ISSB?

ISSB is the standard-setter created by the IFRS Foundation to give investors a global baseline for sustainability and climate disclosures. Its standards IFRS S1 and IFRS S2 build on the TCFD recommendations. Each country decides whether and how to adopt them.

What is TCFD?

TCFD was a task force set up by the Financial Stability Board that issued recommendations on how companies should disclose climate-related risks and opportunities. Its four pillars are governance, strategy, risk management and metrics and targets. Many national and international requirements are based on them.

A practical approach to sustainability reporting

• Work out which requirements apply to each entity, such as ESOS, SECR, CSRD or ISSB-based rules
• Build one data set for energy, emissions and other metrics, and reuse it across reports
• Set clear owners for data collection, review and sign-off
• Align reporting boundaries and methods across reports where the rules allow
• Track changes to rules and update processes in good time
• Keep evidence that supports each number

Frequently asked questions

What is ESOS in simple terms?

It is a UK scheme that requires large organizations to audit their energy use every four years and identify ways to save energy.

What is SECR in simple terms?

It is a UK requirement for certain companies to report their energy use and greenhouse gas emissions in their annual report.

What is the difference between ESOS and SECR?

ESOS is a four-yearly energy audit that is notified to the Environment Agency. SECR is an annual disclosure within the directors' report.

Does ESOS apply to small businesses?

No. It applies to large undertakings. Small and medium-sized enterprises are generally outside it unless they are part of a large group.

Is TCFD still in use?

The task force stopped work in 2023, but its recommendations remain widely used and sit inside later standards such as those from the ISSB.