Every connection to the national electricity network is given its own identification number - the National Meter Identifier (NMI). You'll need this number if you change your electricity retailer.
The NMI is used to:
Your NMI stays the same unless the location of your electricity network connection point changes. For example, if a building is demolished and a new meter is installed.
The NMI is associated with an electricity network connection point, so when you move you'll have a new NMI at your new location.
When the installer gets the meter the NMI will be on the meter.
The installer will then do the necessary paper work to get the meter added to the address and if necessary get the previous NMI removed from the address.
You should not have to do anything.
Please click the like button if you appreciate my answer