Would your Scope 3 numbers survive an auditor's questions?

Timing

You have done the hard work. Spend data is exported, suppliers are mapped to emission factors, and a Scope 3 total sits in your sustainability report. But if an auditor asked why certain costs were excluded, which consolidation approach you used, or which country's emission factor applies to a foreign supplier, would the answers be on paper?

For most organizations, Scope 3 is the largest part of the carbon footprint and the hardest part to calculate reliably. Category 1, purchased goods and services, is often a big share, and where small methodological choices add up to large differences.

Client context
With more than 900 employees, Timing is one of the largest employment agencies in the Netherlands. For more than 25 years, it has placed people in sectors such as food, production, logistics and government.

Timing calculated its own Scope 3 emissions for reporting year 2025 using a spend-based approach: financial transactions were linked to sector codes and emission factors from a reliable public database.

With the footprint feeding into both external reporting and internal reduction targets, Timing wanted independent confirmation that its methodology and calculations were in line with the GHG Protocol. They asked TOSCA to act as a critical second pair of eyes before the numbers were finalized.

The challenge
A spend-based calculation looks simple: spend × emission factor. The difficulty lies in everything around that formula. Every choice, from which costs to include to which sector and country a supplier belongs to, directly affects the outcome.

Timing faced questions many organizations recognize:

• Is the methodology complete? Does it reflect all five GHG Protocol principles: relevance, completeness, consistency, transparency and accuracy?
• Is the boundary clear? Is it documented which entities are included and established which emissions fall under Scope1 and 2?
• Are exclusions justified? Which financial costs can be left out, and which are actually purchased services that must be included?
• Are sector codes and emission factors right? Do they match the real nature of each purchase and the country where the activity took place?
• Is it future-proof? Can the calculation be repeated, compared year on year and show real reduction progress?

Our approach
TOSCA ran a focused review in three steps, based on the GHG Protocol Scope 3 Standard.

• Methodological review. We assessed the calculation method as a whole: guiding principles, organizational boundary, exclusions, spend coverage, base year and recalculation policy, and quality control.
• Sample check of the calculations. We recalculated a selection of cost items line by line. For each, we verified that the assigned sector code matched the actual nature of the purchase, that the right country-specific emission factor was used, and that the Excel formulas worked as intended.
• Actionable feedback. Corrections and suggestions were added directly in the client's own file, together with a clear list of open tasks. A concise findings report explained each point with a concrete recommendation.

The outcome
The review confirmed that Timing's calculations were built on a solid foundation, and gave clear, practical steps to bring the methodology fully in line with the GHG Protocol. Timing now has a Scope 3 approach it can explain and defend with confidence, ready for repeatable annual reporting and a growing role in its emission reduction strategy.

“Mapping your Scope 3 emissions is one thing, but you also want to be sure that the choices and calculations behind them are methodologically sound. TOSCA's review gave us a critical assessment of our approach and clear insight into concrete areas for improvement. That gives us confidence in the quality of our figures and a stronger foundation for our future reporting and reduction targets.”

Lianne Kuiper, Projectmanager Facility Services & Ambassadeur MVO

Ready to put your Scope 3 to the test?
Whether you calculated your footprint in-house or with a tool, an independent review shows where your methodology is solid and where it needs strengthening, before an auditor or stakeholder asks.

TOSCA helps organizations with Scope 3 calculations and methodology in line with the GHG Protocol and the requirements of CSRD and CO2 performance ladder. Curious how robust your numbers are? Feel free to give us a call.