FWIW - i have seen assessments go up in arrears (so mum is owed back pay) but generally if a lower assessment is received, it's received from now, not going backwards, so it's unlikely it would be backdated and taken off you
god i feel dense. I read what you typed, and i don't even understand it.
does that mean, if he DOES put in his tax returns, and the CS assessment shows he has paid too much, does that mean, i will not have to pay back the difference? Sorry to be so thick, but i find that so hard to believe. I don't doubt YOU brigsy, i am just so unsure about money in general, and so scared of debt.

i haven't received any CS yet, and we REALLY could use it, but i'm scared to spend it (if and when it arrives) - until i understand what you put.

the debts i have incurred with CL (due to his incorrect calculations in the past) i find very upsetting. I've tried hard all my life NEVER to be in debt, to live within my means, go without stuff, in order to pay my bills. So to have had TWO CL debts (one took me the last three years to pay back, the second one, i only received a month ago) - is a really big kick in the guts, for me. Neither of them were to do with me, both were to do with incorrect figure HE gave CL. But it a black mark against my name.