How do I fill gaps in Scope 3 data without making numbers up?
Use the GHG Protocol's two tools for gaps: proxy data, a similar activity's figure standing in for the missing one, and extrapolation, scaling up from the suppliers or months you do have. Label every filled figure, state its basis, and report the share of each category that is filled rather than measured.
Step 1: find out which gaps matter
Rank Scope 3 by rough size first, using spend or tonnes bought. A gap in a supplier that is 30% of your purchases needs real data; a gap in office stationery can be filled with a spend-based estimate and left there. Effort should follow size.
Step 2: choose the filling method
- Proxy: use data for a similar material, process or region when the exact one is missing, for example a national average steel factor when the mill gives none. Say what the proxy is and why it is close.
- Extrapolation: scale from a part you have to the whole, for example from suppliers who replied to those who did not, or from nine months to twelve. Only valid when the missing part is similar to the part you have.
- Spend-based: price multiplied by an economic factor, when you have neither quantities nor a proxy. Keep it for small or hard categories.
Step 3: grade and disclose
The Scope 3 Standard asks you to describe data quality by how representative the data is in technology, time and geography, how complete it is and how reliable. In practice, for each category, show the share that is supplier-specific, the share that is proxy or extrapolated, and the share that is spend-based. Next year, aim to move the largest filled shares to measured data.
What crosses the line into making numbers up
- Filling a gap and not saying so.
- Using a factor from a different unit (per piece applied to kg) or a different material because it gives a lower number.
- Extrapolating from your three greenest suppliers to all the rest.
- Setting an unknown category to zero instead of estimating it or stating that it was excluded and why.
Worked example: extrapolating supplier replies
- Purchases from 20 similar component suppliers: ₹5 crore
- 8 suppliers replied, covering ₹3 crore of spend, with 300 t CO2e attributable to your purchases
- Intensity of the replies: 300 / 3 = 100 t CO2e per ₹1 crore
- Extrapolated for the other ₹2 crore: 2 x 100 = 200 t CO2e
- Category total: 500 t CO2e, of which 200 t (40%) is extrapolated and disclosed as such
If the non-responders make a different product or use a different process, extrapolation from these replies is not valid; use a proxy or spend-based figure instead.
What Senseible does here
Senseible gives a Scope 3 line a figure only when its quantity and unit match an approved factor for its category and material; otherwise the line shows Needs Data, so gaps stay visible instead of being filled silently. It does not create proxies or extrapolations for you.
Sources: GHG Protocol Corporate Value Chain (Scope 3) Standard (2011), chapter 7, collecting data and filling gaps, GHG Protocol Technical Guidance for Calculating Scope 3 Emissions (2013)
Last reviewed 2026-10-15.