The first aim of this article is to present a characterization of the techno-mathematical literacies needed for effective practice in modern, technology-rich workplaces that are both highly automated and increasingly focused on flexible response to customer needs. The second aim is to introduce an epistemological dimension to activity theory, specifically to the notions of boundary object and boundary crossing. We draw on ethnographic research in a pensions company and focus on data derived from detailed analysis of the diverse perspectives that exist with respect to one symbolic artifact, the annual pension statement. This statement is designed to facilitate boundary crossing between company and customers. Our study shows that the statement routinely failed in this communicative role, largely due to the invisible factors of the mathematical-financial models underlying the statement that are not made visible to customers or to the customer Enquiry Team whose task is to communicate with customers. By focusing on this artifact in boundary-crossing situations, we identify and elaborate the nature of the techno-mathematical knowledge required for effective communication between different communities in the pensions company, and suggest the implications of our findings for workplaces more generally. (Contains 3 footnotes and 3 figures.)