This paper deals with a data model of a software system used to manage library patrons. This system is known as a circulation system and is usually developed within a library management system. The paper discusses functionalities of a circulation system that allows circulation at the level of library consortium. Based on these functionalities, a data model is made that contains all necessary data for managing library users, both local users and users from other libraries within the consortium. The presented model was used in the development of one particular circulation system, but consideration of the following can be useful in the development of any other circulation system as well.