All electrical work should be tested therefore the results should (might as well) be recorded and given to the client.
Plus relevant fire alarm documentation.
New circuits are notifiable to the Local Authority.
If the installer is 'registered' for self-notification (stupidly called self-certification) then following the certificate for the work from the installer, you will receive a Certificate of Compliance from his registration body.
If the installer is not registered, then YOU should inform the L.A. and pay a hefty fee before the work commences and, depending on what they want, eventually receive a Certificate of Completion from them.
It's not supposed to make sense.