It’s fair to say it varies a lot but here is the official line.
Planning permission - how long does it take
Local planning authorities are expected to make a decision on planning applications as quickly as possible.
The statutory determination period for validated planning applications, which local planning authorities should not exceed, is 8 weeks for straight-forward planning applications, 13 weeks for unusually large or complex applications, and 16 weeks if the application is subject to an Environmental Impact Assessment (EIA).
The determination period can be extended whereby agreement in writing with the applicant.
If the determination period is exceeded, the applicant can appeal to the Secretary of State, although this in itself can take some time.
Where an extension has not been agreed, the Government’s ‘planning guarantee’ commits that no application should take more than a year, including any appeal. In practice this means the applications itself should be decided in no more than 26 weeks, allowing a further 26 weeks for any appeal.
Where an extension has not been agreed, the applicant does not appeal, and the application remains undetermined after 26 weeks, the planning fee will be refunded to the applicant.
The Growth and Infrastructure Act 2013 gives the Secretary of State power to 'designate' local planning authorities if their performance in handling major planning applications is below an acceptable standard. Local planning authorities under special measures have applications determined by the planning inspectorate and lose a proportion of the application fee. Special measures designation is reviewed annually to allow improving authorities to regain their determination powers.
Delays can be caused by incomplete applications, applications that are not in an appropriate form, payment of fees, the timing of planning committee meetings, and so on. To ensure that there are no such delays, it is wise to seek pre-application advice from the local planning authority who can clarify the form of the application required and the information that it may require. If it is necessary for the application to be determined by the local planning committee (rather than by planning officers under delegated authority), they will be able to advise about the timing of meetings and whether the applicant might make representations to the committee.
Planning performance agreements can be prepared for complex applications, or applications where the statutory timescale is likely to be exceeded. These are voluntary undertakings that enable local planning authorities and applicants for planning permission to agree the timescales, actions and resources necessary to process a planning application. They are not intended to be legally-binding contracts, but are in the spirit of a ‘memorandum of understanding’.
The Department for Communities and Local Government publish development control statistics which provide historical data about how long local authorities take to make a decision once a planning application has been submitted.