The successful business has to manage its operations based on seamlessly integrated information systems. In practice, no single solution fits all, so most of the companies are to implement more than one information system based on business needs and availability. What makes the difference is how interoperable are the deployed systems between each other. In this study the importance of critical information to be exchanged is examined. A taxonomy model for a successful application of interoperable Enterprise Information System is proposed. The findings include users' information requirements, business needs, and interoperable systems' information requirements.