The number of millionaires in the UK has fallen to its lowest point since the 2008 global financial crisis, as tax hikes and the threat of a potential wealth tax fuel an exodus of high-net-worth individuals. In 2025, more millionaires left Britain than any other nation, with 16,500 departing, taking an estimated $91.8 billion in wealth with them .

The Numbers: A "Warning Signal" for the UK

According to new figures released by the Adam Smith Institute based on Office for National Statistics data, Britain now has an estimated 442,000 sterling millionaires, representing a 7% decline from 2024 .

The think tank attributed the drop to a combination of falling real asset prices, a low household savings rate, and the emigration of high-net-worth individuals . Mitchell Palmer, an economist at the institute, called the decline "a warning signal," noting that "every millionaire that leaves means less capital for British businesses, fewer international connections, and weaker entrepreneurial spirit in the economy" .

The Wealth Tax Factor

The Possibility of a New Levy

The outflow comes as speculation intensifies over a potential 2% tax on wealth over £10 million. New Prime Minister Andy Burnham has refused to rule out introducing such a levy, stating in an interview with Gary Lineker that the government "may have to ask for a little more" tax at some point .

Business leaders have warned that uncertainty alone is already doing damage. Nigel Green, CEO of deVere Group, said: "A wealth tax that has not been proposed is already doing damage... Money does not sit around waiting for legislation. It moves the moment a government signals it is willing to go there" .

The Counter-Narrative: "Patriotic Millionaires"

In a striking contrast, 120 self-described "patriotic millionaires" —including former footballer Gary Lineker, musician Brian Eno, and film director Richard Curtis—have written to Burnham urging him to tax them more . The group supports a 2% wealth tax on assets over £10 million, arguing "we can afford it" and that a "primary source of untouched capital investment is sitting with us, in untaxed potential" .

The CEO's Appeal: "Stay and Build"

Martin Ott, CEO of the $1 billion tax platform Taxfix, acknowledged that wealthy UK-based clients are eyeing an exit . However, he appealed to them to stay, arguing it is their "social responsibility to invest in their country" .

"Saving taxes is one thing, but at the same time, you also have a social responsibility to make sure you invest in a country," Ott said. He warned that if founders and high earners leave, it will weaken the very ecosystem they thrived in, causing a "brain drain" and making Britain less attractive for future entrepreneurs .

The Political Calculus

With the UK's tax burden at its highest since the Second World War, the debate over wealth taxation sits at the centre of the new government's economic strategy. Critics argue that tax hikes and the abolition of the non-dom regime are already driving away the very people whose investment and enterprise the country needs for growth . Proponents of wealth taxes, including the signatories of the millionaire letter, argue these measures are necessary to fund public services and reduce inequality .

For Burnham, the challenge is balancing competing pressures: the desire for new revenue to fund public services, the risk of accelerating the wealth exodus, and the economic reality that wealth is highly mobile and can relocate quickly to jurisdictions offering greater security and lower taxes .