MPRN also known as Meter Point Reference Number
You will receive a gas bill, whether that be online or paper format every quarter (if you pay direct debit or on receipt of your bill), or you will receive it once per annum (if you are on a pay as you go/ prepayment meter). On this gas bill you will be able to find your MPRN.
When switching to a new supplier they will either ask for the MPRN or the MPAN (Meter Point Administration Number). This is to ensure the supplier has the correct meter for your address.
If you do not have a bill to hand, you can get it by calling the national grid on:
0870 608 1524