"While the yields from HMRC's work in this area have increased it needs to evaluate what approaches are the most effective and to understand the outcomes it achieves."
Of this estimate, which covers more than one tax year, £1.1 billion of this relates to the use of marketed avoidance schemes. HMRC believes that around 15% of high net worth individuals have used at least one scheme.
HMRC has a special unit to collect tax from high net worth individuals who have assets of £20m or more. It raised approximately £416m from its compliance work with this group in 2015-16.
6,000 issues currently under enquiry have been open for more than 18 months, 4,000 of which have been open for more than three years.
In 2014-15, an estimated 6,500 high net worth individuals paid over £4.3 billion in tax. This included £3.5 billion in income tax and national insurance (1.3% of the total revenue for those taxes) and £880 million in capital gains tax.
In addition to the work of the high net worth unit, since 2009 HMRC has recorded yield from high net worth individuals of around £450 million. Around half of this – £230 million – has come from its work in tackling marketed avoidance schemes. A further £80 million relates to fraud investigations and around £140 million from the use of offshore disclosure facilities.
In the last five years, HMRC has investigated and closed 72 cases relating to high net worth individuals, however only two cases were criminally investigated and passed to the Crown Prosecution Service, just one of which was taken forward and successfully convicted.
Amyas Morse, head of the National Audit Office, said: "The tax affairs of the wealthiest in society are complex, making it harder for HMRC to ensure that they are paying the right amount of tax. HMRC's specialist team gives it a better understanding of the tax affairs and behaviours of these taxpayers. While the yields from HMRC's work in this area have increased it needs to evaluate what approaches are the most effective and to understand the outcomes it achieves."