Guidance for developers of assurance arguments has generally focussed on issues concerning content, logical flow and structure. The use of natural language to express an argument can lead to problems with understanding the nature of the claims, with scope and with potentially obscure logical inferences. These problems can occur even if natural language is combined with the use of graphical notations to communicate the structure of an argument. In a supply chain, these problems are compounded by the involvement of numerous suppliers, each with his own “idiolect”, which makes it difficult to integrate assurance data for components into the system argument, to evaluate it as evidence or to reuse it across projects. In this paper, we present work to develop controlled language and structured expressions to improve communication within and across domains and to provide some automated validation of assurance arguments.