Abstract Background Apart from a person’s physical functioning, the early identification of social context indicators which affect patient outcomes - such as environmental and psychosocial issues - is key for high quality and comprehensive care at home. During a home care assessment, a person’s biomedical and functional problems are typically considered. Harder to define concepts, such as psychosocial well-being or living arrangements, are not routinely documented, even though research shows they also affect functioning and health outcomes. The purpose of this study is to develop and test a concise, integrated assessment (BelRAI Social Supplement) that evaluates these social context indicators for persons receiving home care to complement existing interRAI- instruments. Methods The development of the BelRAI Social Supplement is a multi-stage process, based upon the revised MRC-framework, involving both qualitative and quantitative research with stakeholders such as; clients, informal caregivers, care professionals and policy makers. The developmental process encompasses four stages: (I) item generation based on multiple methods and content validation by a panel of stakeholders (II) assessing feasibility and piloting methods, (III) early evaluation, and (IV) final evaluation. Stage II and III are covered in this paper. Results During Stages I and II, a testable version of the BelRAI Social Supplement was developed in an iterative process. In Stage III, 100 care professionals assessed 743 individuals receiving home care in Flanders between December 2018 and December 2019. Using inter-item correlation matrixes, frequency distributions and regular feedback from the participants, the BelRAI Social Supplement was improved and prepared for Stage IV. The updated version of the instrument consists of four main sections: (1) environmental assessment; (2) civic engagement; (3) psychosocial well-being; and (4) informal care and support. In total, the BelRAI Social Supplement contains a maximum of 76 items. Conclusions The ...