One of the current research trends in Enterprise Resource Planning (ERP) involves examining the critical factors for its successful implementation. However, there is limited beyond system implementation, focusing on flexibly of ERP to respond to changes in business. Therefore, this study explores a combination system, involving an ERP system and informality, which focus on providing a company with efficient and flexible performance simultaneously. The paper aims to understand the constraints of using a single ERP system, and to define a new system corresponding to these problems, which is achieved by studying four Chinese companies operating in different industries. The study reveals that an ERP with pre-determined business activities cannot react promptly to unanticipated changes in a business. Incorporating informality into an ERP can react to different situations by using different procedures that are based on the practical knowledge of frontline employees.