This chapter examines the financial management and accounting systems required for the effective and sustainable operation of Research Infrastructures (RIs). It highlights how the hybrid nature of RIs demands both robust financial accounting for transparency and management accounting for planning and control. The chapter outlines the structure and purpose of core financial statements, the specific features of RI revenues, costs, and funding models, and the implications of diverse legal frameworks. It also explores cost-analysis tools essential for strategic decision-making. Overall, it emphasises that sound financial governance is critical to ensuring long-term viability, accountability, and efficient resource allocation in RIs.