Sixty of the UK's richest people collectively contributed more than £3 billion a year in income tax, the BBC has learned.
The amount of income tax they paid was roughly equivalent to two-thirds of all the extra spending Labor incurred in its program earlier this year.
Each of the 60 people had an income of at least £50m a year in 2021/22, but many will have earned much more and are also likely to pay significant sums in other taxes.
There are fears that tax rises planned in this month's Budget could drive out the very rich, damaging the UK's finances. Labor has ruled out any changes to income tax, but Chancellor Rachel Reeves has left the door open to further tax rises.
A Treasury spokesperson said the government was determined to “address injustices in the tax system”.
Swiss banking giant UBS predicted in July that the UK would lose half of its millionaires by 2028, partly due to a shift to low-tax countries.
The Institute for Fiscal Studies said the Treasury must be aware that a small number of these super-rich leaving the country would create a “relatively large hole in its finances”.
But the Green Party argued that claims that taxing the rich more would push them out of the UK were not credible.
The BBC reported last month on concerns within the Treasury that one of the main fundraisers for these pledges, the scrapping of the non-dom scheme, would raise far less money than initially hoped .
The removal of this system, which allows a UK resident to register abroad for tax purposes, was initially estimated to cost £1 billion.
Government ministers also said the previous Conservative government left a £22bn “black hole” in the public finances.
This has led to discussions within the government about possible tax rises in the next budget, and in August the chancellor refused to rule out a rise in capital gains tax.
Stuart Adam, senior economist at the IFS, said reports of wealthy people leaving the UK were anecdotal so far.
But he warned that it would not take a mass exodus to cause problems in public coffers, because “tax payments are very concentrated on a small number of people”.
“There is clearly a risk that Rachel Reeves needs to think about,” Mr Adam said.
“Some of the speculated tax changes are very concentrated on those at the top of the income distribution.”
There could “be more at stake for these people than just the income tax they pay”, as the individuals in question would likely pay significant amounts in other forms of taxation such as capital gains, added Mr. Adam.
Green Party co-leader Carla Denyer has warned against taking threats from the super rich to leave the country seriously.
“This didn’t happen when changes were made to non-dom status in 2017,” she said.
“There are many reasons why the wealthy choose to live in the UK, including work, family and culture, and many are happy to pay a little more if it means a happier, healthier society.”
The figures, which were compiled by HMRC, were obtained through freedom of information laws and relate to 2021/22, the latest year for which data is available.
That year, the UK received a total of £225 billion in tax revenue, with contributions from some 33 million taxpayers.
The 60 people with incomes above £50 million made up just 0.0002% of UK taxpayers and together paid 1.4% of the income tax receipt.
HMRC initially blocked the publication of this information on the grounds that disclosing the figures would identify the individuals in question.
But the authority agreed to release the data after further requests from the BBC.
The IFS said one way to deter wealthy people from leaving the UK could be to introduce an “exit tax”.
Some other countries “say if you leave the UK we will tax you on any gains you accrue while you're here, even if you don't sell the asset until later,” Mr Adam said.
“And symmetrically, we will exempt people who have accumulated gains before coming to the UK, even if they sell assets while they are here.”
A Treasury spokesperson said: “We are tackling the unfairness of the tax system so we can raise the revenue needed to rebuild our public services.
“That’s why we are scrapping the outdated tax regime and replacing it with a new, internationally competitive regime based on residency and aimed at attracting the best talent and investment to the UK.”
