This article looks at the issue of management tools that have been “taken on board” by SSE organisations (and more precisely in the voluntary sector) and their compatibility or incompatibility with the organisations’ principles. It aims to fill a gap in the available studies on SSE enterprises, in particular voluntary organisations with employees, by examining how they use these tools and the effects on their members including both volunteers and employees. Based on a case study of the French Red Cross (18,000 employees, 56,000 volunteers and 600 social and health care establishments in 2014), the authors show that the use of tools to manage economic performance raises not only a question about their legitimacy but more pertinently a question about organisational identity.