This article sheds new light on the development of complementary currencies. Based on a comprehensive survey of the literature, the study questions conventional interpretations of these social innovations. The article challenges the view that money is the only feature that complementary currencies have in common. The author argues that in addition to the ways in which connectivity takes place, a characteristic feature of these systems is that they operate within boundaries. Territoriality, limits to convertibility and other features distinguish them from other unofficial currencies such as Bitcoin. Short case studies illustrate that these boundaries are interdependent. This theoretical framework offers a tool for the analysis of complementary currencies and a perspective on the creation of new types of such systems.