Worked on the Hospital_Management_System repository to deliver an invoicing enhancement that integrated service items into the billing process. Focused on Java development and object-oriented programming, the work involved linking the Service class to invoices and implementing a method to calculate total amounts based on included services. This update improved financial accuracy by ensuring invoice totals reflected all billable services, streamlining the customer invoicing workflow and reducing manual reconciliation. The codebase was refactored for maintainability by modularizing service-related calculations and updating data models. The approach emphasized software design principles, resulting in a more robust and accurate invoicing system for users.