From the following source: revenuebenefits.org.uk/universal-credit/guidance/existing-tax-credit-claimants/tax-credit-debt/
Paying back tax credits debt – moving to UC
Under legislation in the Welfare Reform Act 2012 and subsequent regulations, DWP have the power to recover tax credit overpayment debts from Universal Credit (UC) payments.
Once the UC award ends, the debt remains with DWP and negotiation for time to pay and hardship will be dealt with by DWP.
The claimant journey
Once the UC claim has been made and the tax credits claim stopped, HMRC should send the claimant a letter TC1131 – ‘Your tax credits overpayments’. An example of this letter can be found here.
HMRC will only transfer ‘safe’ debts to DWP which means if a person is appealing or has an active dispute against a debt it should not transfer. As debts can transfer to DWP at different times, claimants may receive more than one TC1131. No action needs to be taken as a result of this letter unless the claimant wants to challenge an overpayment.
Any time to pay arrangement (normally by direct debit) that the claimant already has with HMRC (or a private debt collector working on their behalf) will be stopped automatically. Claimants who are repaying by standing order will need to cancel it with their bank.
Joint claims
Tax credits operate joint and several liability which means HMRC can ask one or both partners to repay a joint debt. However, their policy set out in COP 26 is that when there is a household breakdown (the couple separate) they will split the debt 50/50 (unless the claimants agree to a different split) and as long as one claimant pays back their 50%, HMRC won’t pursue them for the remaining 50% even if their ex-partner does not pay.
Our understanding is that, where claimants separate, HMRC will split the debt 50/50 before transferring the 50% to DWP for recovery from the single claimant’s UC. Each person should be notified separately of their part of the debt.
Recovery rates in UC
There are 3 main rates of recovery in UC:
15% of the standard allowance (non-fraud debt if you don’t have earned income)
25% of the standard allowance (non-fraud if you have earned income)
40% of the standard allowance (fraud classified debt or you are repaying a hardship payment)
Which recovery rate applies depends on the claimant’s circumstances and can change from month to month. It was announced in Budget 2018 that the 40% rate of recovery will be reduced to 30% from October 2019.
(Sorry for the long post!)