Enterprise modelling is an essential component in defining an enterprise, such as a manufacturing facility, an end-item distribution company, a financial institution, or a university department. The goal of our enterprise modelling research is to create generic representations of enterprise knowledge that can be reused across a variety of enterprises. Towards this end, we have been developing the TOVE (TOronto Virtual Enterprise) ontology [Fox and Griininger 94]. TOVE provides a rich and precise representation of generic knowledge, such as activities, resources, time, and of more enterprise oriented knowledge such as cost, quality, products, and organization structure. In this paper, we present enterprise modelling as a new area of application for theoretical work in reasoning about action. We give an overview of the problems encountered in enterprise modelling and the requirements that they impose on any theory of action. We outline our approach to these problems using an extension to the situation calculus.