This study presents the development and implementation of an Integrated Cashless Rent Management System (ICRMS) for Kampala Capital City Authority (KCCA), the administrative body responsible for managing Uganda's capital city. KCCA manages a substantial portfolio of commercial and residential properties, markets, and public spaces from which it collects rental income as a significant component of its internally generated revenue. Persistent challenges with manual and fragmented rent collection processes including revenue leakage, late payment, inadequate record-keeping, corruption, and limited management visibility provided the impetus for developing a comprehensive digital rent management solution. The system was developed using the Agile Scrum methodology and integrates a tenant registration module, rent billing and invoicing module, mobile money and bank payment gateway, automated reminder and notification module, and a management analytics dashboard. Evaluation was conducted through a structured survey of 138 respondents including KCCA property management staff, tenants, and IT administrators, supplemented by analysis of revenue data from 24 months before and after implementation. The findings demonstrate that the ICRMS resulted in a 43.7% increase in rent revenue collection efficiency, a 71.2% reduction in payment disputes, and a 58.4% reduction in rent collection administration costs. Regression analysis identified system integration quality, user experience design, and mobile money compatibility as the strongest predictors of system adoption success. The study concludes that the ICRMS represents a transformative improvement in KCCA's property revenue management and provides a replicable model for other Ugandan public authorities.