A prominent City economist has cautioned of a potential fiscal shock in the coming months due to an increasing number of billionaires leaving Britain, which could destabilize public finances. Simon French, chief economist at Panmure Liberum, suggested that the tax self-assessment returns due in January could be significantly lower than forecast if a substantial number of high-profile UK taxpayers have relocated offshore.

The warning comes as hedge fund manager Chris Rokos, estimated to be worth £3 billion and identified as the UK's third-highest taxpayer, prepares to shift his residency to Greece. This departure follows that of steel magnate Lakshmi Mittal and Egyptian businessman Nassef Sawiris, who moved out of the UK after reforms to the non-domicile tax regime were implemented in 2024.

Official data indicates a decline in the number of millionaires residing in the UK, falling to 442,000—the lowest figure since 2007. This represents a decrease of approximately 7% compared to the previous year. While some of this reduction can be attributed to a downturn in asset values, an increasing number of wealthy individuals are reportedly choosing to leave the country.

This trend coincides with speculation about potential new tax increases aimed at funding government spending commitments, which include expanding social housing, reforming social care, and augmenting defense budgets. Both shadow Chancellor Andy Burnham and Chancellor John Healey have previously expressed a desire for the UK to be a hub for wealth creation, with Healey stating his aim to make the country one "of wealth creation."

While some members of the Labour party have advocated for an annual wealth tax, its implementation is considered unlikely. The Treasury is more expected to adjust capital gains tax rates. Previous changes to capital gains tax by former Chancellor Rachel Reeves, which raised rates for basic and higher-rate taxpayers, were described by experts as providing a one-off boost but potentially jeopardizing public finances long-term. This is due to investors and landlords altering their behavior to minimize their tax liabilities, which may lead to lower overall receipts in the future, particularly as the wealthy depart the UK to avoid higher taxes.

Research from Wealth Club indicates that over 60% of millionaire investors have contemplated leaving the UK due to concerns about rising tax burdens.