Cooperatives play a vital role in supporting local public economies, requiring continuous guidance, oversight, and internal audits to ensure compliance, transparency, and accountability. In Palembang City, the Department of Cooperatives and Small-Medium Enterprises (SMEs) oversees 457 registered cooperatives, including 107 Merah Putih Cooperatives. However, monitoring procedures and internal audit reporting—such as Annual Member Meeting (RAT) submissions—have historically been conducted through physical, paper-based workflows. This manual approach resulted in slow information exchange, disorganized paper archives, high risks of document loss or damage, and operational inefficiency. To resolve these challenges, this study designed and developed a Web-Based Information System for Monitoring and Internal Auditing of Merah Putih Cooperative Reporting. The system was developed using the classic Waterfall SDLC model, covering requirements analysis, architectural modeling (Context Diagram, Data Flow Diagram Level 1, Entity Relationship Diagram, and Data Dictionary), web-based implementation (PHP and MySQL RDBMS), black-box functional testing, and system maintenance. The resulting application seamlessly integrates three distinct user roles: Cooperative Users, Report Administrators, and Audit Administrators. Comparative analysis reveals that the digital platform reduced report processing and verification times from days to real-time status updates, eliminated physical archival overhead, and significantly improved data accuracy. Comprehensive black-box testing verified that 100% of functional modules executed correctly without logic errors.