There is no law or legisaltion that prevents suppliers billing for consumption over a year old.
There is however a billing code of practise that many suppliers have signed up to. (not all have however).
The billing code in prevents suppliers billing for consumption over 1 year old in certain conditions, there are also conditions where it does not apply. If you feel this may affect you perhaps let us know the situation with any and all pertinant facts that you have and we cna help you figure out if it applies or not.