Business software systems have often grown over years and contain specific knowledge which is essential for the enterprise using the software. However, it is difficult to adapt these software systems to the rapidly changing hardware and software technologies. This so-called legacy problem is extremely cost intensive when a change in the software itself or the hardware platform is required due to a change in the business processes of the enterprise or the hardware technology. Thus, a common problem in business software is the cost effective analysis, documentation, and transformation of business software. In this paper, we concentrate on the transformation issue of software systems and propose an incremental process for transforming monolithic business software into client-server architectures. The internal logical structure of the software system is used to create software components in a flexible way. The transformation process is supported by a transformation toolset which preserves correctness and functionality.