Tax credit renewal, why do i have to renew when i dont receive them, in fact owed them money

[EleanorReally]

and my youngest is 19 and left sixth form a year ago?

Presumably you need to confirm your income details for the last year and estimates for this year so they know how much it is reasonable to pay back to them? If you want to know, ring them and ask.

you cant get through!
i have managed to renew, though it seems pointless

You can always write to them if you can't get through on the phone.

Or the other tip is to phone them 5 minutes before the closing time, that usually works.

I haven’t claimed for 8 years since my claim went tits up and I accrued an overpayment. When I spoke to them this year they said my claim is due to be cancelled in October this year (I am still paying back the overpayment for another 2 years).