To identify weaknesses in cost tracking and reporting approaches that hinder reliable cost-efficiency evaluation (as observed in many evaluation reports) and to provide practical recommendations for strengthening future assessments, EBD International conducts comprehensive analyses of the cost-efficiency of emergency response and development projects. Evaluating cost-efficiency is indispensable to ensure resources are used effectively, maximize benefits for target populations, and inform more strategic decisions in program planning and funding. We identified the most important and still feasible lessons (to be) learned and applied, which have the potential to help organizations in designing projects that allow for reliable cost-efficiency evaluation.