The total annual tax credit entitlement for families earning more than £50,000 is estimated to be approximately £45 million.
This estimate is based on finalised incomes and circumstances of families benefiting from tax credits in 2007-08 which is the most recent year available. These statistics are available at:
http://www.hmrc.gov.uk/stats/personal-tax-credits/ctcw-tax-credit-final-may09.pdf
Household income has been calculated based on income used to calculate tax credit entitlement and will therefore disregard in-year income rises of less than £25,000.
The total annual tax credits entitlement of these families will differ slightly from the additional revenue to the Exchequer of excluding them from tax credits, because of effects on over- and under-payments. Analysis of these effects is available only at disproportionate cost.
To reduce total annual tax credit expenditure by £400 million, it is estimated that the second income threshold would need to be reduced to around £31,000.