A land owner or developer who has already obtained an outline permission has to get their reserved matters approved before carrying out the development. A reserved matters submission is not in legal terms a planning application. It does not have to be made on an application form (but they usually are) and ownership certificates are not needed. There is no legal requirement for neighbours to be consulted on the application, but in practice most local planning authorities (LPAs) do so. The application should be in accordance with the principles of development that have already been approved at outline application stage, e.g. if a certain floor area for the building is specified, though a slight or small deviation might be considered acceptable by the LPA. Not all the reserved matters have to be submitted in one application and the application does not necessarily have to cover all the development, e.g. if the outline approval is for several buildings, only the details for one building could be submitted. For large development this could and often does involve several phases of development over a number of years. It is possible for more than one set of details to be approved – the developer or land owner would then have to decide which one to build.
More information can be found on the Planning Portal.