Scope 3 covers the indirect emissions in your value chain across 15 GHG Protocol categories, from purchased goods to business travel, waste and investments. WeZero supports activity-based calculation using physical quantities and spend-based estimation using cost-based factors, applying UK Government (DESNZ) conversion factors for the correct reporting year. The AI expense allocator turns a spend spreadsheet into Scope 3 estimates with a full review and override workflow, and supplier engagement tools let key suppliers report their own data. Results feed the same dashboards, targets, SECR narratives and Carbon Reduction Plan as your Scope 1 and 2 data. The core Scope 3 calculator is free.