"The purpose of this companion guidance is to provide practical and hands-on technical guidance on developing a theory of change as an integral part of the United Nations Development Assistance Framework (UNDAF) process. It should be read as a complement to the 2017 UNDAF Guidance and relates closely to the other seven companion guidance papers on programming principles, the UN Vision 2030, the Common Country Analysis (CCA), communications and advocacy, capacity development, monitoring and evaluation, and funding to financing. A theory of change is a method that explains how a given intervention, or set of interventions, are expected to lead to a specific development change, drawing on a causal analysis based on available evidence. In the UNDAF context, a thorough theory of change helps guide the development of sound and evidence-based programme strategies, with assumptions and risks clearly analysed and spelled out." (Introduction)