First you should get an idea about how fast the meter moves when cooking or heating then, when there is someone in the other flat and preferably when it is cold, turn everything off (except for any pilot light) and see if the meter keeps moving. If gas is being used when everything is off downstairs, either there is a gas leak or, as you suspect, the upstairs flat is sharing the meter. If so, it is possible that there is a sub-meter and you do need to raise the matter with the landlord. If a tenant suspects that they are not going to be paying for gas, they may use more than they can afford. Without a submeter and readings, you can estimate how much is owed to you by metering typical usage downstairs and subtracting that from the bill.

I suspect that my Son is paying for Gas to both his and upstairs flat. He lives in an old Leeds Terrace House which has been converted into 2 flats. The bill for end of Nov toMarch was reallt high - in that time he was away for a month.

On checking last week I could only find 1 gas meter which had an outlet pipe into his property & then continued into the flat above.

I have contacted Gas Supplier who say I need to take it up with Landlord & also ask other flat if they have a Sub Meter?? They are away & letting agency have not got back to me.

Suggestions please