At the CHE-VERIFY Joint General Assembly, Rona Thompson (NILU) introduces the progress and plans for the VERIFY WP4. The overarching goals of WP4 are to deliver estimates of CH4 and N2O surface to atmosphere fluxes, including anthropogenic as well as natural sources, and to build this capacity into a pre-operational system, the Community Inversion Framework (joint development with WPs 3 and 2, described via an Algorithm Description Document, ADD and a Product Description Document, PDD). WP4 will also improve the understanding of the processes driving surface-atmosphere fluxes of CH4 and N2O, and reduce the uncertainties in their budgets and trends at national, regional and continental scales.