Developed and integrated a new Ontario Health Premiums and Surtaxes feature for the BuildCanada/CanadaSpends repository, expanding the platform’s tax calculation capabilities. The work involved designing modular TypeScript functions to accurately compute health premiums and surtaxes, ensuring compliance with Ontario tax regulations. These functions were seamlessly incorporated into the existing tax calculation workflow, improving both accuracy and maintainability. The approach emphasized backend calculation logic and clear commit traceability, supporting future enhancements for additional jurisdictions. No major bugs were reported during this period, reflecting careful implementation and testing. The project demonstrated skills in TypeScript, software development, and domain-specific tax calculation.