If you want to be certain that the existing use of a building is lawful for planning purposes or that your proposal does not require planning permission you can apply for a "Lawful Development Certificate" (LDC).
It is not compulsory to have an LDC but there may be times when you need one to confirm that the use, operation or activity named in it is lawful for planning control purposes.
You can apply to your local council for an LDC via the Planning Portal online application service. The application must provide sufficient information for the council to decide the application or else it may be refused. You will have to pay a fee.
Often the issues involved in LDCs are complex and if you decide you need to apply for a certificate you might benefit by obtaining professional advice. Your LPA's planning officers can also help. They will tell you about the sort of information needed to support your application.
If your application is partly or wholly refused or is granted differently from what you asked for, or is not determined within the time limit of eight weeks, you can appeal. Appeals are made to the Planning Inspectorate.