This guideline was prepared as part of the GGGI's efforts to develop frameworks and methodologies for development impact estimation of its country-level and global activities. It outlines the concepts, approaches, and methodologies used to estimate expected strategic outcome (SO) impacts of current projects and to develop approximate future targets for impacts based on GGGI's planned future activities. It discusses how their SOs are placed within the organization’s Theory of Change and aligned with their priority activity areas and the Sustainable Development Goals (SDGs). The report also describes how intended SO targets are estimated in the GGGI Strategy 2030 and covers how the SO impacts of projects/outputs in GGGI countries will be reported.