Introduction: In 2017 a Research in Practice (RiP) Change Project, conducted with RiP Partners from 19 local authorities in England, explored the development of a tool for calculating the financial costs of delivering services for young people who are on the ‘edge of care’.The Change Project method applies an action research approach to developing evidence-informed, practical resources by bringing together experts from across practice and research. You can read more about this methodology and other Change Projects at www.rip.org.uk/change-projects This project was a collaboration between RiP, North Yorkshire Children’s Services, and academics at the Centre for Child and Family Research (CCFR), Loughborough University (Lisa Holmes and Helen Trivedi, now based at the Rees Centre, University of Oxford).