Transition finance offers a flexible approach for development partners to respond to the changing financial needs of developing countries undergoing transition. The transition finance ABC methodology, part of the transition finance toolkit, provides methodological guidance, metrics, data references and analytical interpretation for users to conduct transition finance diagnostics and country studies.The paper is organised along the sections: assessing, benchmarking and counselling. The first section, assessment, outlines an economic and socio-political mapping of the country and helps to identify the specific transition a country is undergoing. Benchmarking, section two, helps to form country peer groups and contrast development finance to these countries. Building on the analytical results from the first two sections, the last section on counselling gives exemplary policy guidance to respond to the observed transition challenges.The current paper extends the existing work on transition finance by providing operational guidance and compelling evidence on how to implement a transition finance approach. The paper follows a three-pronged methodology (the ABC methodology for transition finance) that allows to Assess, Benchmark and Counsel transitioning countries and development partners, with a focus on deriving specific recommendations for DAC members and partner countries and informing the work of other development stakeholders. A1 -Understanding the economic and socio-political setting A2 -Examining the transition context and its implications A3 -Analysing the financing mix B -Benchmarking B1 -Identifying peer countries in the transition finance landscape B2 -Conducting a comparative analysis B3 -Learning from good (and bad) practices C -Counselling C1 -The co-operative approach C2 -The competitive approach C3 -The case for a renewed partnership Annexes Glossary References