You must contact the Building control office to give formal notification of completion not less than 7 days before the work is due to be finished.
When the work is completed (excluding decorating and furnishing) you must arrange for a final site inspection.
A completion certificate will be issued providing the work is satisfactory, all Building control monies paid and any relevant documents have been received.
This is an official document which should be kept safe as without it you may have difficulty selling your property.