The advent of the internet is revolutionizing the financial services industry. In the future, electronic banking (EB) will become a strategic factor, evolving from mere transaction banking to the provision of individual, highly customized solutions. For this new way of EB it is essential to have a profound knowledge about the customer. In this paper, we discuss customer modeling as a solution for establishing a central repository, which can provide services for various EBapplications. We show that those generic customer models should include both, knowledge, e.g. about risk-affinity, attitude towards net present value and affinity towards special products, represented as preferences, but also plain information, like age and know-how. Furthermore, we suggest an approach for oneto- one-banking, which, in a first step, completes customer models from given information and thereby lays ground for the ongoing step two, in which user specific actions are inferred.