Scope 3 sounds daunting: the GHG Protocol lists 15 categories. A PPN 006 Carbon Reduction Plan asks for five of them, plus all of your Scope 1 (fuel you burn, refrigerant leaks) and Scope 2 (electricity you buy). Here is what each of the five covers and how a small supplier can measure it.
Category 4: Upstream transportation and distribution. Deliveries to you, and transport you pay for between your own sites, made by other companies. Records: courier and haulier invoices, ideally with weights and distances. Where you only have the amount spent, an estimate from spend is a start, labelled as such.
Category 5: Waste generated in operations. The waste your sites produce, by type and how it's treated (landfill, recycling, composting). Records: waste contractor invoices and waste transfer notes, which usually give tonnes or bin lifts.
Category 6: Business travel. Staff travel for work in vehicles you don't own: trains, flights, taxis, hire cars, private cars on expenses, and hotel nights. Records: expense claims (mileage and fuel type), travel booking reports and receipts.
Category 7: Employee commuting. Staff travel between home and work, and home working if you include it. Records: a short staff survey (how far, how often, by what mode), repeated each year.
Category 9: Downstream transportation and distribution. Transport of goods you've sold to customers, where you don't pay for it. Many service businesses have little or none; say so in the plan rather than leaving it blank. Records: customer collection details or carrier data.
Turning records into tonnes. Multiply each activity (kWh, litres, miles, tonnes) by the UK government's conversion factors for the reporting year, as PPN 006 requires. Activity data beats spend: a figure from miles travelled is more reliable than one from pounds spent, and buyers can tell the difference.
How big are these in practice? (Example data) In the demo organisation, Sampleshire Facilities Ltd (1 April 2025 to 31 March 2026), employee commuting was 18.7328 tCO2e, almost as large as its Scope 1 of 20.1781 tCO2e. Downstream transportation was 6.1536 tCO2e and business travel 3.9349 tCO2e.
Keep the trail. Keep every invoice, survey and claim behind each figure. If a buyer or auditor asks how you got a number, you can show them.
In Scopterra, each Scope 3 entry is linked to its record and shows whether it was measured, calculated or estimated from spend. You can also invite up to 25 suppliers to share their own data.