The Treasury will recoup more than £5bn in unpaid tax from Britons with Swiss bank accounts under a deal between the UK and Switzerland signed last night.
Switzerland's strict secrecy laws have made it a safe haven for the rich, but the Government is cracking down on offshore tax evasion.
In 2013, Swiss banks will hand over a one-off levy of more than £5bn to settle past tax liabilities of Britons with cash in the country.
From then on, Switzerland will impose a withholding tax of 48% on income such as interest and 27% on capital gains such as shares rising in value. It is unclear how much this will raise because Britons may move their assets elsewhere.
The agreement was signed in Zurich by Dave Hartnett, the permanent secretary at HM Revenue & Customs. "The world has changed for tax evaders," he said.
Chancellor George Osborne said: "The days when it was easy to stash the profits of tax evasion in Switzerland are over."