Both your electricity and gas supply are allocated a unique reference number associated with your home. These numbers are different from your meter reference number or meter serial number which will change if you have a new meter installed, for example, a Smart Meter.
Your electricity supply point number is called an MPAN (meter point administration number), is always shown on your electricity bill, and looks like this:
Supply Point Number
Your Gas supply point number is called an MPRN (meter point reference number) and is an 11 digit number and is always shown on your gas bill.