The high net worth unit of the UK tax authority, HM Revenue and Customs, gathered a record £220 million (around $335 million) of extra tax last year.

HMRC’s HNW unit, which deals with the tax affairs of 5,800 people with assets in excess of £20 million, increased its tax enquiries by 10 per cent in the 2012/2013 tax year, having collected £200 million in 2011/2012.

“HMRC’s HNW unit provides the specialist attention they require in ensuring the wealthy pay the tax they owe. This government has reinvested almost £1 billion in HMRC and expects them to deliver almost £22 billion in 2014/2015,” said David Gauke, exchequer secretary to the treasury.

Since it was established in 2009, the HNW unit has increased its revenues from the UK’s richest taxpayers every year, raising a total of £665 million in additional tax over the last four years. This revenue is in addition to the taxes HMRC normally collects from this group of wealthy individuals and is the result of enquiries, the UK tax authority said.