Although many auditing software generated by the ERP system is considered reliable, auditing personnel find difficulty in using the system because of their insufficient knowledge concerning information technology. Apart from the lack of knowledge and unfamiliarity with the software, the ERP systems themself are complex enough for their application (Tsai and Feng 2004, Lanza 2005). Most firms deal with business processes through semi-manual methods, like the use of Microsoft Excel (Huang and Chuang 2005). Therefore, an easy-to-use computer auditing system developed exclusively for a certain ERP system is deemed expected and needed. It is on this concern that this research was anchored. Specifically, this research aims to achieve the following purposes: (1) to explore the crucial control items of the purchasing and expenditure cycle in meeting the conditions of SOX 404; (2) to develop a computer auditing system based on the recognized control items and requirements of SOX 404; and (3) to validate the applicability of the system using an ISO/IEC 9126 model in meeting organizational needs.