In recent years, climate risk, stakeholder pressure and sustainability regulations have shifted carbon accounting from a niche exercise of big corporations into a core business tool. While historically dominated by FTSE 100s and global supply chains, carbon accounting is now creeping into the SME (small-to-medium enterprise) market.
Why the change? Three forces are converging:
- Supply chain and procurement demands — larger companies increasingly require emissions data from suppliers, even small ones.
- Investor and customer expectations — transparency on emissions is becoming a differentiator in winning contracts or finance.
- Technological progress — tools are emerging that make carbon accounting far less burdensome than before.
This means that SMEs can no longer view carbon accounting as optional “nice to have.” Starting early can give you competitive advantage, improve efficiency, and help future-proof your business.
What Is Carbon Accounting (and How Does It Work)?
At its core, carbon accounting is about measuring greenhouse gas (GHG) emissions associated with your business activities, converting them into common units (usually CO₂ equivalent, or CO₂e), and aggregating them into reports.
The standard framework used by many organisations is the Greenhouse Gas Protocol, which classifies emissions into three scopes:
- Scope 1: Direct emissions from your operations (e.g. fuel combustion, company vehicles).
- Scope 2: Indirect emissions from purchased energy (electricity, heating, cooling).
- Scope 3: Other indirect emissions (e.g. waste, business travel, upstream and downstream supply chain emissions).
In practice, many organisations begin with Scopes 1 and 2 (because the data is easier to capture) before tackling the more complex Scope 3 categories. The typical approach is:
- Collect data — energy bills, fuel use, travel records, expense data, supplier data.
- Apply emission factors — these convert units (kWh, litres, km) into CO₂e using recognised tables.
- Aggregate and report — sum up emissions across categories and present the total footprint.
- Set reduction targets and track progress — use the baseline as a reference point.
There are many challenges: data gaps, inconsistent supplier reporting, methodological choices, and boundary setting (which activities to include). Recent research points out 24 distinct “accounting challenges” in the transition to net zero strategies (for example, reconciling life-cycle assessments, double counting, dynamic emissions over time) . But these challenges are no longer a barrier — the new generation of carbon tools is helping SMEs overcome them.
Carbon Reporting Pressure on SMEs
Although UK regulation (for now) primarily mandates carbon and energy reporting for large firms via the Streamlined Energy and Carbon Reporting (SECR) regime, SMEs are increasingly pulled into the net of carbon reporting through supply chains.
Large clients, public bodies or institutions may demand emissions disclosures from their vendors. That means even if you’re not legally obliged to report, you may lose tenders or contracts if you can’t show your carbon footprint or reductions.
Furthermore, global reporting standards (e.g. the ISSB or the successor to TCFD) are pushing for climate disclosures that could cascade down value chains.
So, SMEs that act early and build carbon capability are likely to outperform those that lag.
Why Carbon Accounting Is Easier Now Than Ever
Historically, carbon accounting was resource-intensive: spreadsheets, manual data collection, consultants, bespoke models. But the landscape is changing rapidly. Modern software tools offer automation, integration, user guidance, and audit-ready reporting.
Key enablers:
- Accounting integration — carbon tools that tie directly into your accounting or bookkeeping system can pull transaction data and reduce manual work.
- Prebuilt emission factor libraries — the software handles conversions and standard methodology for you.
- User education and support — embedded training modules, guidance, and handholding make carbon accounting more accessible.
- Supplier data collection and collaboration — tools now help SMEs request emissions data from their partners and embed sustainability across supply chains.
One such tool making a splash in the SME space is Sumday.
Sumday: Bringing Carbon Accounting into the SME Fold
Sumday is a modern carbon accounting platform designed for accountants, bookkeepers, and businesses. A key differentiator is its integration with Xero — many SMEs already use Xero for bookkeeping, so Sumday can pull in general ledger data directly, reducing friction.
In its partnership with Xero, Sumday is offering 12 months’ free access to its carbon accounting tools for eligible Xero users, enabling them to jumpstart their carbon journey.
Some highlights of Sumday:
- Seamless data import — linking directly with your Xero data means less manual data entry and fewer errors.
- Audit-ready reports — Sumday supports preparing carbon inventories and reports consistent with global standards.
- Educational resources — Sumday hosts a “Sumday Academy” to help users learn carbon accounting concepts at their own pace.
- Supply chain engagement tools — SMEs can then engage with their own suppliers to collect emissions data.
Because so many small businesses already use Xero (or intend to), Sumday’s integration is a compelling route to making carbon accounting low friction and cost effective.
How SMEs Can Get Started — A Practical Roadmap
Here’s a simple step-by-step approach for any SME thinking of embarking on carbon accounting:
- Choose your tool or approach
Assess whether to use software (like Sumday or alternatives) or launch a basic spreadsheet. If you’re using Xero, Sumday is a strong option thanks to integration and free access periods. - Define the boundary and scope
Decide which emissions to include: start with Scopes 1 and 2, and gradually expand into Scope 3. - Gather data
- Energy bills (electricity, gas)
- Fuel and vehicle use
- Business travel (flights, vehicles, rail)
- Supplier data (if available)
- Waste and waste transport
- Map transactions to emission factors
Use standard conversion tables (e.g. government conversion factors) or let software do it. - Aggregate and validate
Run the numbers, check for anomalies, and reconcile totals with expectations. - Set reduction goals and action plans
Identify your biggest emissions categories and propose interventions — e.g. switching to green electricity, reducing travel, supplier engagement. - Report and communicate
Present your footprint internally and externally. If required, provide emissions data to clients or tenders. - Track, iterate, and improve
Re-measure periodically, track against targets, and refine your processes.
With tools like Sumday, many of these steps (especially mapping, aggregation, report formatting) are automated, significantly reducing the barrier for SMEs.
