Complex IT projects can be carried out more economically and precisely using procedural models or phase concepts. The authors, both legal professionals, draw on extensive practical experience with large projects and the risks associated with managing IT projects and their legal consequences. Based on the phase concept of the public sector for the development of IT programs, as well as the procedural model of the Federal Ministry of the Interior for IT initiatives, essential areas of action, responsibilities, types of contracts, and their legal significance or impact are illustrated through case law and literature. IT practitioners receive valuable insights for their daily problem-solving.