Child Tax Credit was paid to help people with the costs of bringing up a child. It is replaced by Universal Credit.

Working Tax Credit was money provided to boost the income of working people that are on a low income, and that work a certain amount of hours per week.

If you owe money back to HMRC for tax credits overpaid, you will probably receive an overpayment letter at some point. In a joint claim, both of you are liable to repay the debt. 

Debt Recovery

Debt Solutuin: An debt solution only writes the debt off for an individual. To write off joint debt, usually a debt write off solution each is required.

Benefit Deduction: HMRC can apply to recover the tax credits overpayment directly from certain benefits, including Universal Credit.