Employees use their own cars for work trips and claim mileage. How do I count those emissions?
Trips in an employee's own car for company work go in Scope 3 Category 6, business travel, because the company does not own or operate the car. Use the kilometres from the mileage claims times a per-km factor for that kind of car, or the litres if you reimburse fuel. Commuting to the usual workplace belongs in Category 7.
Which scope
- Employee's own car, used for a client visit, site visit or bank trip, paid by mileage: Scope 3 Category 6.
- Company-owned or leased car the company runs: Scope 1, from the fuel bought.
- Daily travel between home and the usual workplace: Scope 3 Category 7, employee commuting, even if the company pays an allowance.
Two ways to calculate
- Distance-based: kilometres claimed times a per-km factor for the car's fuel and size. This is the usual method because claims already record kilometres.
- Fuel-based: if you reimburse fuel bills, litres times the fuel factor, such as 2.31 kg CO2 per litre of petrol or 2.68 for diesel (IPCC 2006 defaults).
Getting a per-km factor you can defend
Divide the fuel factor by a realistic mileage. A petrol car doing 15 km per litre emits about 2.31 / 15 = 0.154 kg CO2 per km. State the mileage you assumed. If claims record the car model, use the model's fuel economy; if not, use one assumption for small cars and one for SUVs and say so.
What to collect from claims
- Date, purpose and kilometres for each trip.
- Fuel type: petrol, diesel, CNG or electric. For an electric car, use kWh per km times the grid factor.
- Whether the trip was already counted elsewhere, such as a taxi on the same route.
Worked example: a year of mileage claims
- Kilometres claimed for work trips: 18,000 km, all petrol cars
- Assumed mileage: 15 km per litre, so 18,000 / 15 = 1,200 litres
- Emissions: 1,200 x 2.31 = 2,772 kg CO2, about 2.8 tonnes in Category 6
The 15 km per litre is an assumption; replace it with the actual fuel economy where you know it.
What Senseible does here
Senseible reads fuel bills and invoices and applies IPCC 2006 factors per litre. Mileage claims are spreadsheets rather than invoices, so keep the kilometre log as the evidence for Category 6 and use Senseible for the fuel bills you reimburse.
Sources: GHG Protocol Scope 3 Standard, Category 6 business travel, IPCC 2006 Guidelines, Volume 2 Energy
Last reviewed 2026-10-20.