The number of adults in Britain with a net worth of at least £1 million fell 7 per cent to 442,000 in 2025, the lowest level since 2008, according to analysis published by the Adam Smith Institute.

The centre-right think tank’s millionaire tracker counts adult British residents with at least £1 million in individual net worth across all real and financial asset classes, including property and pensions, measured in constant prices. It is built by applying a statistical model to Office for National Statistics household wealth data, which the institute puts at about £10.75 trillion in 2024.

The count passed one million in 2020 and reached 1.07 million in 2021. It has fallen in each of the four years since.

The institute attributes the decline to higher interest rates and a lack of confidence in the British economy reducing the inflation-adjusted value of pension pots and high-end London property, a low household savings rate, and the emigration of high net-worth individuals.

In its report, the Adam Smith Institute said: “There has [also] been a well-documented trend of high net-worth individuals either leaving Britain or no longer choosing to move here. Millionaires are leaving the country for a number of reasons, including the abolition of non-dom tax status, high levels of general taxation, and a hostile culture for wealth creators.”

HM Revenue & Customs data does not show a sharp fall in the non-dom population before the regime was scrapped. Its latest statistics put the number of individuals claiming non-domiciled status at 73,700 in the tax year ending April 2024, down 400, or 0.5 per cent, on the previous year. Those figures cover the period before April 2025, when the remittance basis was replaced with a residence-based regime exempting foreign income and gains for up to four years for new arrivals and for those returning after a decade abroad.

Business Matters reported in October that consultancy Chamberlain Walker estimated 1,800 non-doms had left Britain since the April 2025 change, a figure the Treasury said was “based on anecdotal evidence we don’t recognise”.

The ONS measures household assets every two years, so there is no official count of individual millionaires. Its latest data records 3.7 million households with net wealth above £1 million, most of it accounted for by house prices.

The Adam Smith Institute is calling on the government to abolish inheritance tax, cut capital gains tax and commission an international competitiveness assessment of the UK’s tax and regulatory treatment of non-doms and high net-worth individuals. It made a similar argument in 2024, when it forecast that Britain would see the largest exodus of millionaires globally.

HMRC data shows 31,500 estates paid inheritance tax on death in the tax year ending April 2023, about 4.5 per cent of people who died. Capital gains tax is charged at the point of sale on assets such as shares, at 18 per cent for basic rate taxpayers and 24 per cent for higher and additional rate payers. Income tax bands are 20 per cent, 40 per cent and 45 per cent.

Allies of Andy Burnham have called on the prime minister to equalise capital gains tax with income tax. Burnham has said he will “look in detail” at equalisation but has made no policy commitment. He has previously suggested abolishing inheritance tax and replacing it with a “care levy” to fund social care reform. He has also declined to rule out a wealth tax, prompting warnings from advisers that speculation alone is pushing capital out of Britain.

Andrew Griffith, the shadow business and trade secretary, said: “Whatever their personal finances, everyone should care about Britain having fewer millionaires to contribute to the tax pot and creating jobs and businesses here. It’s a competitive world and when young and ambitious people are voting with their feet and leaving your country that’s a shameful sign.”