We’ve just discovered that there was a “Single occupancy” rate applied to our account of Thames Water. We live in a block of flats, 2 bed (family with 2 children). There is an additional account holder for the last 10 years and we assumed that they are informed there’s more than one person (spouse joined to initially single occupied property)? Like it usually happens, we see the amount due online and pay it in full and did this for a decade without a second thought. What are we supposed to do? Obviously we have to inform them but what is likely to happen to us? We are absolutely terrified of the consequences. According to this years’ charges we would need to pay approx £79 more a year. We just don’t know if they backdate the additional charge and what is likely to happen. Desperate for advice, thanks!