Senior Full Stack Developer (React / C# .NET) Contract: Initial 3-Month Engagement (Long-Term Programme) IR35 Status: Outside IR35 Location: Hybrid Working - Approximately 1 day per week in Birmingham (flexible based on project requirements) Rate: £500 per day Outside IR35 Overview We are seeking experienced Senior Full Stack Developers to join a major business transformation programme focused on modernising platforms, data capabilities, and core business processes. This is an opportunity to play a key role in the design, development, and delivery of enterprise-scale solutions, working across both front-end and back-end technologies while contributing to data migration, integration, and technical design activities. The successful candidates will be strong engineers with deep expertise in React and C#/.NET, capable of operating across the full technology stack and collaborating closely with Product Owners, Business Analysts, Architects, and Testing teams within an Agile delivery environment. Key Responsibilities Full Stack Development Design, develop and maintain modern web applications using React and C#/.NET. Deliver robust front-end experiences with a strong focus on usability and performance. Build scalable and maintainable back-end services, APIs, and integrations. Contribute across the full technology stack where required. Support development best practices, code quality, and technical standards.Data & ETL You will support key data transformation initiatives, including: Migration of existing artefacts into target data models. ETL solution design and implementation. Development of data ingestion processes and pipelines. Integration with target platforms, applications, and databases. Validation, transformation, and reconciliation of legacy data.Technical Design & Architecture Working alongside Architects and technical stakeholders, you will contribute to: Solution architecture discussions. System and integration design activities. Environment and deployment strategy. Technical assessments and feasibility analysis. Definition of implementation approaches and delivery options.Agile Delivery Participate in workshops, discovery sessions, and sprint planning activities. Refine business requirements and technical features. Provide estimates and support work sizing exercises. Contribute to sprint delivery and release activities. Collaborate closely with Product Owners, Business Analysts, Architects, and Test teams. Essential Skills & Experience Extensive commercial experience as a Full Stack Developer. Strong expertise in React and modern front-end development practices. Strong experience with C#/.NET and back-end API development. Experience designing and developing enterprise-grade applications. Proven experience working on data migration, ETL, or integration projects. Strong understanding of relational databases and data modelling. Experience contributing to technical design and architectural discussions. Comfortable working within Agile delivery teams. Excellent stakeholder engagement and communication skills. Desirable Experience Experience working on large-scale transformation programmes. Exposure to cloud-based architectures and modern deployment approaches. Experience integrating with multiple enterprise platforms and third-party systems. Familiarity with Jira, Confluence, and Agile tooling