In recent years there has been a growing interest in the stance of the social sciences towards the deployment of proliferating amounts of transactional data. This paper is intended to be a resource for stocktaking reflections on these issues. We bring together the views of a number of sociologists, geographers, and business researchers working on these issues, along with input from practitioners with expertise in the use of transactional and administrative data. We do not develop an argument here but rather lay out issues that need to be addressed in future reflections on transactional data, focusing on (i) what is rendered visible and invisible, (ii) embedded temporal and spatial relationships, and (iii) modes of expertise and theoretical resources.