The department said that the figure, out of the 1.2 million high-rate taxpayers who were due to lose all or part of their benefit, was higher than expected.
Where one parent is earning £50,000, part of the child benefit would be taken away, increasing steadily to 100 per cent of the benefit for those earning £60,000 or more.
HMRC Chief Executive Lin Homer said that this will mean cost-savings to the taxpayer.
"Because it has worked better than expected, the administration charge of implementing this change we think is only going to be 50 per cent of what we expected," she added.
"We think it will cost us £11 million to raise the £2 billion that this change will raise."
Previously, Ms Homer said that as of early December, 680,000 people had already looked at information on HMRC's website.
Posted by Thomas Fletcher