Carbon accounting: a guide for UK accountants and bookkeepers

Published Thursday 11 June 2026

Table of contents

• Why is carbon accounting important for UK businesses?
• Understanding Scope 1, 2, and 3 emissions
• How to do carbon accounting
• UK carbon reporting requirements
• Carbon accounting standards and frameworks
• How carbon accounting benefits your practice and clients
• Carbon accounting tools and software
• Help your clients go green with Xero
• FAQs on carbon accounting

Key takeaways

• Growing advisory opportunity: with Streamlined Energy and Carbon Reporting (SECR) already in force and the UK Sustainability Reporting Standards (UK SRS) published in February 2026, your clients will increasingly need help measuring and disclosing their carbon footprint.
• No specialist science background needed: the core skill set is data collection, calculation, and reporting, which maps directly onto what you already do every day for your clients.
• Start with Scope 1 and 2: SECR mandates reporting on direct and energy-related emissions. Scope 3 (value chain) is voluntary for now, but investor and supply-chain pressure is making it harder to ignore.
• The right tools: cloud accounting software like Xero centralises the financial data you need, and dedicated carbon accounting apps plug straight into your existing workflow.

Climate-related regulation, investor expectations, and client demand are reshaping the advisory landscape. Carbon accounting sits at the intersection of all three, and accountants and bookkeepers are well placed to lead the conversation.

Why is carbon accounting important for UK businesses?

Carbon accounting is the process of measuring, recording, and reporting the greenhouse gas (GHG) emissions produced by a business. It works alongside financial accounting to give stakeholders a fuller picture of an organisation's performance and risk exposure.

For your clients, the drivers are both regulatory and commercial. The Streamlined Energy and Carbon Reporting (SECR) framework already requires qualifying companies to disclose their energy use and carbon emissions in their annual reports. SECR applies to any UK company that meets at least two of three thresholds: 250 or more employees, turnover of £36 million or above, or a balance sheet total of £18 million or above.

Beyond compliance, the picture is shifting quickly. The UK Sustainability Reporting Standards (UK SRS) S1 and S2 were published in February 2026, closely aligned with International Financial Reporting Standards (IFRS) S1 and S2. These are voluntary for now, but the Financial Conduct Authority (FCA) is consulting on making them mandatory for listed companies from January 2027.

Investors, lenders, and larger supply-chain partners are already asking for carbon data. Businesses that get ahead of these expectations protect their reputation, reduce greenwashing risk, and often uncover cost savings through more efficient energy use. For your practice, this represents a natural extension of the advisory work you already provide through sustainability accounting.

Understanding Scope 1, 2, and 3 emissions

The GHG Protocol, the most widely used carbon accounting standard, divides emissions into three scopes. Understanding these categories helps you advise clients on where to focus their measurement efforts and reduction strategies.

Scope 1: direct emissions

Scope 1 covers emissions from sources the business owns or directly controls. In a UK context, the most common examples include company vehicles running on petrol or diesel, natural gas used for heating office or warehouse space, and on-site generators or industrial processes.

Scope 2: indirect energy emissions

Scope 2 covers emissions from purchased electricity, heating, or cooling. For most UK businesses, this means the electricity powering their premises and any district heating they use. These emissions happen at the power station or heat source rather than at the business itself, but the business is responsible because it created the demand.

Scope 3: value chain emissions

Scope 3 captures everything else across the value chain. This includes business travel (flights, rail, taxis), purchased goods and services, waste disposal, employee commuting, and the downstream use of products the business sells. Scope 3 typically makes up the largest share of a company's total emissions, sometimes exceeding 80%.

SECR mandates reporting on Scope 1 and 2 emissions. Scope 3 remains voluntary under UK regulations, but it's increasingly expected by investors, large corporate clients, and industry bodies. Advising clients to start capturing Scope 3 data now positions them well for future requirements.

How to do carbon accounting

The calculation itself is straightforward: multiply activity data by the relevant emissions factor to get a CO2 equivalent (CO2e) figure. The challenge lies in collecting accurate data and choosing the right method. Here's how to approach it step by step.

1. Collect activity data

Start with the business data your clients already have: utility bills, fuel receipts, mileage logs, travel bookings, and procurement records. Much of this sits in the accounting system, which makes your role particularly valuable. You can pull energy spend, fleet fuel purchases, and travel expenses directly from the general ledger.

2. Apply emissions factors

Emissions factors convert activity data into CO2e figures. The UK government publishes updated conversion factors each year through the Department for Energy Security and Net Zero. The 2025 DEFRA conversion factors are the current reference set. For example, the 2025 factor for diesel is 2.57 kg CO2e per litre.

3. Choose a calculation method

There are three main approaches, and your choice depends on the data available and the level of accuracy required.

• Spend-based method: converts financial spend into emissions using average factors per pound spent. It's the quickest way to get a baseline, but it's the least precise because it relies on sector averages rather than actual consumption data.
• Activity-based method: uses physical data such as kilowatt hours of electricity, litres of fuel, or kilometres travelled. This produces more accurate results and is preferred for compliance reporting.
• Hybrid method: combines both approaches, using activity data where it's available and spend-based estimates to fill the gaps. The GHG Protocol recommends this as the most practical starting point for most organisations.

For most of your clients, the hybrid method strikes the right balance between accuracy and effort. As data collection improves over time, you can shift towards a fully activity-based approach.

UK carbon reporting requirements

The UK's carbon reporting landscape has several layers. Knowing which rules apply to which clients helps you scope your advisory services accurately and avoid over- or under-reporting.

Streamlined Energy and Carbon Reporting (SECR)

SECR has been in force since April 2019. It applies to quoted companies, large unquoted companies, and large limited liability partnerships (LLPs) that meet at least two of the following thresholds: 250 or more employees, annual turnover of £36 million or above, or a balance sheet total of £18 million or above. Note that these SECR thresholds remained unchanged despite the separate Companies Act 2006 threshold changes that took effect in April 2025.

Qualifying businesses must report their UK energy use, associated Scope 1 and 2 GHG emissions, and at least one intensity ratio (for example, tonnes of CO2e per £1 million of revenue) in their directors' report. Scope 3 reporting is encouraged but not required. Further guidance is available in the UK government's environmental reporting guidance.

UK Sustainability Reporting Standards (UK SRS)

The UK Endorsement Board published UK SRS S1 (general sustainability disclosures) and S2 (climate-related disclosures) in February 2026. These standards are closely aligned with IFRS S1 and S2, making them familiar territory if your clients also operate internationally.

UK SRS is voluntary for now. However, the FCA is consulting on proposals to make it mandatory for UK-listed companies from January 2027. Even for clients not directly in scope, understanding these standards helps you prepare them for potential future requirements or voluntary early adoption.

Voluntary reporting

Smaller businesses below the SECR thresholds have no legal obligation to report emissions, but many choose to do so voluntarily. Drivers include supply-chain requirements from larger customers, investor due diligence, customer expectations, and a genuine desire to reduce environmental impact. Initiatives like the Business Climate Hub provide free tools for small and medium-sized enterprises (SMEs) to measure and report their carbon footprint.

Carbon accounting standards and frameworks

Several international frameworks shape how carbon data is measured, verified, and disclosed. You don't need to be an expert in all of them, but a working knowledge helps you guide clients towards the right approach for their size, sector, and ambitions.

• GHG Protocol: the most widely adopted standard for corporate carbon accounting. It provides the Scope 1, 2, and 3 framework and detailed guidance on boundaries, methodologies, and reporting. A multi-year revision is currently underway to update the standards for the first time since 2004.
• ISO 14064: an international standard for quantifying and verifying GHG emissions. Useful for clients who need third-party assurance or who want to demonstrate the credibility of their data to stakeholders.
• Science Based Targets initiative (SBTi): helps companies set emissions reduction targets aligned with climate science. Increasingly referenced by investors and procurement teams as a marker of genuine commitment.
• Carbon Disclosure Project (CDP): a global disclosure platform used by thousands of companies to report environmental data. Many large corporates request CDP responses from their suppliers, so your mid-market clients may encounter this through their supply chain.

Think of these as reference points rather than competing systems. The GHG Protocol provides the measurement methodology, ISO 14064 adds verification, SBTi sets the ambition level, and CDP is the disclosure mechanism.

Together, they give your clients a credible and coherent approach to carbon management.

How carbon accounting benefits your practice and clients

Adding carbon accounting to your service offering isn't just about doing the right thing environmentally. It's a practical business decision that creates value for your practice and strengthens client relationships.

• New advisory revenue stream: carbon accounting is a specialist service you can charge for, whether as a standalone engagement or bundled with existing compliance work. Clients need help with data collection, calculation, reporting, and ongoing monitoring.
• Deeper client relationships: offering sustainability advisory positions you as a strategic partner rather than a compliance provider. Clients who rely on you for carbon reporting are less likely to move to a competitor.
• Greenwashing risk mitigation: inaccurate or misleading carbon claims carry real reputational and legal risks. Your rigour with data gives clients confidence that their disclosures are defensible.
• Operational efficiency for clients: the process of measuring emissions often highlights energy waste, inefficient processes, and cost-saving opportunities. A thorough carbon audit frequently pays for itself through reduced utility bills and operational improvements.
• Future-proofing your practice: as sustainability reporting requirements expand, practices with established capabilities will be better positioned to serve growing demand without a scramble to upskill.

The accountants and bookkeepers who move early will have a head start in building expertise, refining their processes, and establishing a reputation in this space. Your existing skills in data management, reporting, and advisory make this a natural fit. Explore more ways to expand your service offering through the Xero accountant and bookkeeper guides.

Carbon accounting tools and software

Manual spreadsheets can work for a first pass, but they don't scale well as your client base grows or as reporting requirements become more detailed. Purpose-built tools save time, reduce errors, and make year-on-year comparison straightforward.

Cloud accounting software like Xero centralises the financial and transactional data that feeds into carbon calculations. Because energy spend, fuel purchases, and travel expenses already flow through the system, you can extract the activity data you need without chasing paper receipts or separate spreadsheets.

Several carbon accounting apps integrate directly with Xero, connecting emissions calculations to your existing accounting workflow. You can browse the available options in the Xero App Store. These tools typically automate emissions factor lookups, calculate CO2e figures from transaction data, and generate reports aligned with frameworks like the GHG Protocol and SECR.

Xero is also committed to its own sustainability journey. You can read about Xero's environmental targets and progress on the Xero sustainability page.

When evaluating tools for your practice, consider how well they integrate with your existing tech stack, whether they support the reporting frameworks your clients need, and how easily they handle multi-entity or multi-site calculations.

Help your clients go green with Xero

Carbon accounting is a practical, revenue-generating addition to your advisory toolkit. The data skills you already have translate directly into this growing area, and the right tools make the process manageable from day one. Start building your carbon advisory capability alongside your existing practice, and help your clients measure what matters.

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FAQs on carbon accounting

Here are some frequently asked questions about carbon accounting that your clients and colleagues may raise.

What is the difference between carbon accounting and financial accounting?

Financial accounting records monetary transactions and produces statements like profit and loss, balance sheets, and cash flow reports. Carbon accounting measures and reports greenhouse gas emissions using activity data and emissions factors. The two disciplines share core skills like data collection, analysis, and reporting, which is why accountants are well suited to offer both.

Is carbon reporting mandatory for small businesses in the UK?

Not currently. SECR applies to large companies and LLPs that meet specific size thresholds. However, many smaller businesses report voluntarily to meet supply-chain requirements, attract investment, or demonstrate their commitment to sustainability. Voluntary reporting is likely to become more common as the UK SRS framework matures.

What are Scope 1, 2, and 3 emissions?

Scope 1 covers direct emissions from sources a business owns or controls, such as company vehicles and gas boilers. Scope 2 covers indirect emissions from purchased energy like electricity. Scope 3 includes all other value-chain emissions, from business travel and purchased goods to waste disposal. SECR requires Scope 1 and 2 reporting; Scope 3 is voluntary but increasingly expected.

How can accountants add carbon accounting to their service offering?

Start by familiarising yourself with the GHG Protocol and SECR requirements. Identify clients who are already close to the reporting thresholds or who have expressed interest in sustainability. Use your existing accounting data to run a pilot carbon calculation, then build out a repeatable process. Carbon accounting apps that integrate with your cloud accounting software streamline the workflow significantly.

What is SECR?

Streamlined Energy and Carbon Reporting (SECR) is a UK regulatory framework that requires qualifying companies to report their energy consumption and greenhouse gas emissions in their annual directors' report. It applies to quoted companies, large unquoted companies, and large LLPs meeting at least two of three size criteria. SECR has been in force since April 2019 and covers Scope 1 and 2 emissions, with Scope 3 reporting encouraged but not mandated.