Network Rail is the trade name used by Network Rail Ltd and its various subsidiary companies. The most prominent subsidiary is Network Rail Infrastructure Ltd (previously named Railtrack plc) which is the owner and operator of most of the rail infrastructure in Great Britain (England, Scotland and Wales). It is not responsible for railway infrastructure in Northern Ireland or for the majority of track used by London Underground.
Network Rail Ltd is a statutory corporation created as a "not for dividend" private company limited by guarantee; Network Rail Infrastructure Ltd was reported in the 2010 annual company report as 100%-owned by Network Rail Ltd. Network Rail Ltd. has no shareholders thus is not owned by anyone but it is subject to various official requirements and directions. Currently the company applies its income to its own purposes (including some donations to charities etc.). The lack of a legal owner makes it liable (as happened with the pre-privatisation Trustee Savings Bank) to any future statute taking it into government ownership and its status as a statutory corporation enables the government to make changes to the company despite not being the legal owner.
Network Rail's main customers are the separate and mostly private-sector train operating companies (TOCs), responsible for passenger transport, and freight operating companies (FOCs), who provide train services on the infrastructure that the company owns and maintains. Network Rail does not itself run passenger or freight services. Ultimately both Network Rail and the train operating companies have the shared responsibility of delivering train services to the travelling public.