Consultative Assistance Systems (CASS) enhance today’s transaction-oriented applications by case-driven, rule-based and interactive components geared towards individual needs of the end-user. ▪CASS supports in the resolution process with rare cases, which are typically complex in nature.▪CASS guides the end-user in finding a solution that covers all legal and economical aspects of each case.▪The example described in this article represents a CASS which supports the complex process of public procurement under the tendering by-laws. The application architecture used in this example can be transferred to many eGovernment scenarios.