The Biggest Challenges with Carbon Accounting for Businesses

What is carbon accounting and why does it matter?

Carbon accounting is the process of measuring, recording, and reporting an organisation's greenhouse gas (GHG) emissions. It is, in many ways, analogous to financial accounting — systematic, standardised, and subject to increasing regulatory scrutiny. Just as financial accounting tracks the flow of money through an organisation, carbon accounting tracks the flow of greenhouse gases associated with its activities.

For UK businesses, carbon accounting has moved from a voluntary exercise to a regulatory requirement. SECR mandates annual reporting for qualifying companies, and the anticipated UK SRS will expand these obligations further. But the value of carbon accounting extends well beyond compliance.

Identifying emission hotspots reveals operational inefficiencies — the site that consumes twice the energy per square metre as comparable facilities, the fleet vehicle that is 40% less efficient than its replacement, the supplier whose embedded emissions are ten times higher than alternatives. These insights translate directly into cost savings and competitive advantage.

Carbon accounting also provides the foundation for credible sustainability commitments. Without reliable measurement, any net zero target, science-based target, or carbon reduction plan is built on guesswork. And as investors, customers, and regulators become more sophisticated in evaluating sustainability claims, the quality of the underlying data matters more than ever.

Despite its growing importance, carbon accounting presents several significant challenges for businesses — particularly those attempting it for the first time or scaling beyond basic Scope 1 and 2 reporting.

Data collection: the universal bottleneck

Ask any sustainability professional what consumes most of their time, and the answer is almost always the same: chasing data.

Carbon accounting requires activity data from across the organisation — electricity consumption from utility bills, natural gas from heating records, fuel from fleet management systems, refrigerant data from maintenance logs, procurement spend from finance systems, travel data from booking platforms, waste data from disposal contractors. Each data source sits in a different system, owned by a different team, arriving in a different format, on a different schedule.

For multi-site organisations, this challenge multiplies. A company with 20 offices might have 20 different electricity suppliers, each with different billing formats and billing cycles. A Multi-Academy Trust might need data from 15 schools, each with its own facilities manager (or no facilities manager at all). A retailer with 50 stores needs consistent data from locations that range from owned to leased, from metered to unmetered.

The traditional approach — sending spreadsheet templates to site managers and chasing responses via email — is slow, error-prone, and demoralising for everyone involved. Data arrives late, in inconsistent formats, with unexplained gaps and anomalies. The sustainability team spends weeks cleaning and reconciling data before a single calculation can begin.

This is the strongest argument for carbon accounting software. Automated data collection — whether through direct integrations with utility providers, AI-powered extraction from PDF bills, or structured data request workflows — can reduce data collection time from weeks to days and dramatically improve data quality by eliminating manual transcription errors.

Scope and boundary definition

Defining what to include in your carbon inventory is more complex than it first appears. The GHG Protocol provides two approaches for setting organisational boundaries — operational control and financial control — and the choice affects which entities, sites, and emission sources you include.

For most UK companies reporting under SECR, the operational control approach is standard: you report emissions from operations over which you have operational control, regardless of ownership percentage. But even within this apparently simple framework, boundary questions arise:

• Do you include emissions from leased buildings where you pay the energy bills but do not own the asset? • What about shared facilities — a co-working space, a shared data centre, a multi-tenant building with a single gas supply? • If you operate a franchise model, are franchisee emissions within your boundary? • When you acquire a company mid-year, how do you handle the partial-year data?

Scope 3 boundary definition is even more challenging. The GHG Protocol defines 15 categories of Scope 3 emissions, but not all will be material to every organisation. The screening process — estimating emissions across all categories to determine materiality — requires judgment, and different organisations can reach different conclusions about which categories to include. Documenting and justifying these decisions is essential for audit readiness.

The practical solution is to start with a clearly defined boundary, document your reasoning, and expand progressively. Your first year might cover Scope 1 and 2 across your directly controlled operations. Year two adds Scope 3 screening. Year three deepens Scope 3 in material categories. This iterative approach is both practical and aligned with regulatory expectations.

Emission factors and calculation accuracy

Applying the correct emission factors is a critical step that introduces both technical complexity and potential error. Emission factors — the conversion ratios that translate activity data (litres of diesel, kWh of electricity) into CO₂e — vary by fuel type, country, year, and methodology.

In the UK, DEFRA publishes annual conversion factors that cover hundreds of activity types. Using the wrong year's factors, the wrong fuel type factor, or the wrong unit conversion can produce materially incorrect results. And because these factors change each year as the grid decarbonises and methodologies are updated, maintaining consistency across multi-year reporting requires careful version management.

For Scope 3, the emission factor challenge intensifies. Spend-based factors (kgCO₂e per £ spent) are inherently less precise than activity-based factors, and the choice of factor set — DEFRA, Exiobase, EEIO — can produce significantly different results for the same spend data. Documenting which factors were used and why is essential for comparability and audit readiness.

Carbon accounting platforms address this by embedding the correct factor sets and applying them automatically based on the activity type and reporting period. This eliminates manual factor lookup errors and ensures consistency across the inventory.

Navigating multi-framework reporting

UK companies increasingly face multiple reporting obligations: SECR annually, potentially CSRD for those with EU operations, CDP disclosure if requested by investors or customers, and SBTi progress reporting if science-based targets have been set. Each framework has different requirements for scope coverage, calculation methodology, disclosure format, and verification standards.

Managing multiple frameworks from the same underlying data set is a significant operational challenge. The emissions numbers should be the same — your Scope 1 and 2 do not change because you are reporting to a different body — but the presentation, context, narrative, and supplementary information differ for each framework.

The most efficient approach is to maintain a single, comprehensive GHG inventory built on GHG Protocol methodology, and then generate framework-specific outputs from that central dataset. A good carbon accounting platform makes this straightforward — one data set, multiple reports, each formatted to the specific requirements of the target framework.

The alternative — maintaining separate spreadsheets for each reporting obligation — is a recipe for inconsistency, duplication of effort, and increasing risk as frameworks evolve and reporting obligations multiply.