This article analyses the work of issuing tickets to queuing customers, thereby contributing to the literature on interactive service work. It draws analytical attention to artful practices through which employees infer ticket orders from local configurations of talk, gesture and bodily movement. It reveals not only the practical reasoning deployed by the service worker, but also the agency of the customer in the course of encounters. Drawing upon video recordings of over 200 separate transactions, the demands of remedying problem orders are analysed to reveal how staff infer and clarify social ‘facts’, such as the customer’s age, their nationality, employment status and willingness to pay the higher ‘Gift Aid’ price. An image of interactive service work emerges that emphasizes the peculiar and skilful articulation of sociological categories in the course of apparently routine low-level work. The concept of ‘inferential labour’ is introduced to capture these processes, which resonates with studies of categorization and emotional labour in interactive service work.