The secrecy, subtlety, and diversity of party-firm relations have proven challenging to synthesise. We introduce a new heuristic framework for the study business donors on the basis of pragmatic, partisan, and social motivations. We illustrate our framework with an analysis of donors to the UK Conservative Party from the property services and construction industries. While actors make it almost impossible to place particular events in our framework, in the aggregate the framework is empirically tractable. We triangulate a study of over twenty years of donations data, news on social events, and qualitative data to argue that the construction industry is motivated by a combination of pragmatic and social motivations, while the property services industry is best described by a combination of the social and partisan motivations.