A growing number of IT organizations pursue a systematic strategy to mature their software operation. These efforts have severe implications for their customers or clients both in terms of opportunities and challenges. As a consequence a number of customer related models have emerged as a supplement to the software process centered maturity models. This paper addresses the improvement of the customer-supplier relation in IT development on a theoretical, a normative, and a practical level. It presents theoretically founded insights into the nature of customer-supplier collaborations. This knowledge is used 1) to evaluate and compare normative models for how to improve customer-supplier relations and 2) to explore practical ways to improve the relation between an IT organization and its customers. The paper is concluded with a discussion of implications for research and practice.