Planning permission is the consent you are required to obtain from your Local Planning Authority to start/complete your proposed building project. The building of an extension, erection of a new build houses/flats, changing the use class of your property or changes to the existing buildings, usually requires planning permission.
The cost of a planning application differentiates across the UK. Currently, a full application for a new single dwelling or extension costs £462, a householder application costs £206 and a lawful development application costs £103 in England.