This document provides guidance for experts evaluating proposals submitted for the Horizon 2020 (H2020) program. It outlines the objectives, roles and responsibilities of independent experts in evaluating proposals against the specified criteria of excellence, impact, and quality of implementation. Experts are responsible for carrying out impartial evaluations of assigned proposals within deadlines and reporting any misconduct. The evaluation criteria and process, including consensus reports, panel reviews, and proposal prioritization are also described.