There is an ongoing pressure on IT service prices based on efficient and effective processes and IT infrastructure on the market. The client demands more (web-based) services that are available on-demand from an optimised, and highly scalable, service provider. For example cloud services especially are not only a technical challenge. They capture the attention of the business and they are the source of growth for the business. Clients and suppliers are searching for the right In-/ Outsourcing level to fulfil these demands. In focus are the business processes and the supporting IT services along the whole supply chain. IT services have also an end-to-end lifecycle with interfaces and different layers (organisation, processes, IT/infrastructure, legal, finance). Existing requirements engineering and management models concentrate only on parts of the IT service requirement lifecycle. There is a need for an end-to-end lifecycle model and the practical management of the IT services. The article regards the definition of service requirements and develops a model for the end-to-end lifecycle management of service requirements and their different layers. The main focus is set on service requirement engineering also as basis of Continual Service Improvement and Knowledge Management. Other parts are topic of the current investigation.