The transition process from the subscription model to the open access model in the world of scholarly publishing brings a variety of challenges to libraries. Within this evolving landscape, the present article takes a focus on budget control for both subscription and publication expenditure with the opportunity to enable the shift from one to the other. To reach informed decisions with a solid base of data to be used in negotiations with publishers, the diverse already-existing systems for managing publications costs and for managing journal subscriptions have to be adapted to allow comprehensive reporting on publication expenditure and subscription expenditure. In the case presented here, two separate systems are described and the establishment of joint reporting covering both these systems is introduced. Some of the results of joint reporting are presented as an example of how such a comprehensive monitoring can support management decisions and negotiations. On a larger scale, the establishment of the National Open Access Monitor in Germany is introduced, bringing together a diverse range of data from several already-existing systems, including, among others, holdings information, usage data, and data on publication fees. This system will enable libraries to access all relevant data with a single user interface.