Tax credits dispute

Hello again, more tedious TC hassles. words fail me.

We have been overpaid TC for 05/06. Have received a demand for payment of ca. £5300. However we only received ca. £4900. Have the bank statements and payslips to prove it I rang up to dispute their figure. TC helpline says the difference is a sum which was set against overpayments in previous years. However I have already got DDs in place to pay off previous years ( ie 03-04 and 04-05) overpayments in full - so they are in effect asking for the same money back twice.

TC helpline referred me to the overpayments no., who referred me back tot the helpline, who could find no record on the system of my agreements to repay previous overpayments.

I got a bit cross then and said that I disputed the amount of overpayment and would not pay anything until I got a bill for the correct amount. They have now sent me a form to fill out (TC846) which says "use this form if we have paid you too much tax credit and you think you should not have to pay it back".

Well the point is they never paid us the money thats in dispute. They kept it and set it against another debt. So should I fill the form out or not. If I ring the TC helpline again, the mental stress wll probably cause the operators head to explode. help.................................................