Lee Carswell developed a Payment Initiation V2 API endpoint for the DEFRA/epr-payment-frontend repository, introducing conditional routing based on RequestorType and updating related DTOs and configurations. He ensured robust functionality by implementing comprehensive unit tests and adhering to SonarQube standards, which improved maintainability and code quality. In the DEFRA/epr-frontend-accountmanagement-microservice, Lee addressed potential InvalidOperationExceptions by adding a null check for organisationData, enhancing data handling reliability. His work demonstrated strong skills in C#, ASP.NET Core, and API development, delivering targeted solutions that increased system flexibility, reduced technical debt, and contributed to safer, more reliable production deployments.