Are all overpayments of tax credits recoverable?
Tax credits are assessed on an annual basis and your total entitlement for a year is not finalised until the end of that tax year. This means that an element of under- and over- payment is built into the system. It is expected that all overpayments will be carried over and recovered during the next tax year.
This means that all tax credits overpayments are recoverable. However, HMRC's 'Tax Credits: What happens if I've been paid too much' guidance (link opens in a new window) states that an overpayment will not be recovered if it was due to a mistake at the tax credit office and not through any error of yours.
If both you and the Tax Credit Office made a mistake, they will decide whether to recover some or all of the overpayment.