In the broadest sense, formulation, or case conceptualisation, is the process of collaborative sense-making. It is something all clinicians are doing constantly, whether formally and consciously or not. Most clinicians are familiar with the general principals and need to formulate as it is a core part of clinical training across most disciplines. Treatment manuals often discuss formulation, but the practical steps involved and the process of developing, building upon and revising formulations are not always provided. In clinical practice, the active use and continued development of formulation during treatment is not always prioritised, especially beyond the initial assessment. This could be due to a number of reasons, such as a potential lack of clarity, understanding or confidence in the use of formulation across treatment, a lack of dedicated time and reflective space for formulation in the context of increasingly busy clinical settings, or a perception that it may be less necessary in the context of treatment approaches that are more structured and prescriptive. This article outlines the use of formulation in family therapy for child and adolescent eating disorders, provides guidance on how to actively include formulation more throughout treatment and discusses why this might be useful.