Part P is the section of the building regulations that covers the electrical installation. It is a legal requirement for all electrical work to meet the Building Regulations. As the homeowner or landlord you must be able to prove that any work carried out meets the regulations by having the work certificated.
Part P applies to newly-built homes and to any changes made to existing installations, including any parts that have been rewired.
To ensure that work is certificated you need to have the work done either via a qualified and registered electrician or you must go directly to the local authority who’ll use one of their qualified and registered electricians to inspect the work at regular stages that suit them, you’ll also get to pay them for the inspection.
More information about Part P and what work must be notified can be found here www.niceic.com/Uploads/File1247.pdf