Carbon accounting and incentive allocation frameworks are a central component of Reducing Emissions from Deforestation and Degradation (REDD+) and in structuring these frameworks, decisions need to be made over how to reach REDD+ objectives in a timely, economically efficient and socially and environmentally sustainable manner. The process of unification or integration of REDD+ projects and subnational efforts into the national system is commonly referred to as 'nesting' or following a 'nested approach'. The strategic importance of the nested approach lies in its utility of coherently integrating various levels of greenhouse gas (GHG) accounting and incentive allocation into the national system while maintaining accounting and environmental integrity. This decision support tool provides overall guidance on establishing national-level REDD+ accounting frameworks within which project or subnational approaches are integrated.