Behavioural insights (BI) are lessons derived from the behavioural and social sciences, including decision making, psychology, cognitive science, neuroscience, organisational and group behaviour. Public bodies around the world are increasingly using BI to design and implement better public policies based on evidence of the actual behaviour and biases of citizens and businesses. This toolkit provides practitioners and policy makers with a step-by-step process for analysing a policy problem, building strategies, and developing behaviourally informed interventions.