Purpose - This paper aims to elaborate the concepts of boundary subjects and boundary objects in constructing and communicating relevant accounting facts for managing product development (PD). Boundary subjects as reflective actors benefit effective accounting enactment, by building a shared understanding about different actors' roles and information needs, and by helping to respond to these needs with new boundary objects. Design/methodology/approach - The paper uses a longitudinal interventionist case study of a machinery manufacturer. The focus of this case study was the production ramp-up phase at the end of a PD program. Different actors' needs were first collected and elaborated by interventionist researchers (boundary subjects). Then accounting prototypes (boundary objects) provided new means of communication. Findings - The findings show that dealing with boundaries is crucial in accounting development. The role of boundary subjects was fundamental in the process of choosing, constructing, elaborating and communicating accounting facts. During this process, accounting prototypes integrated new accounting facts, the boundary subjects mitigated the boundaries and the boundary objects focused and restricted communication about accounting facts. Research limitations/implications - The paper tests the pragmatic constructivism approach by examining accounting enactment under uncertainty and ambiguity. The study refines pragmatic constructivism in terms of boundaries, boundary subjects as actors and boundary objects. Practical implications - The intentional use of boundary subjects and objects as communication platform could push a more active inclusion of business controllers as active business partners. Originality/value - The paper contributes to the literature on accounting development by highlighting the use of boundary subjects and boundary objects as fundamental mechanisms in constructing and communicating accounting facts.