The UK Exchequer would be £4.3 billion ($8.6 billion) a year better off if the government scrapped the domicile rules, claims a report by Tax Research which was commissioned by the Trades Union Congress. The sum is equivalent to more than a penny off income tax and has prompted TUC leader Brendan Barber to call for the government to remove the tax benefits for non-domiciliaries. According to HM Revenue & Customs, the UK's tax authority, 112,000 people claimed non-domicile status on their self-assessment tax form in the year to April 2005. This was a rise of 74 per cent from 2002. And it is understood this figure may now exceed 200,000 as more individuals sought relief under this year’s Offshore Disclosure Facility, introduced by HMRC, which expired in June. HMRC has stated it will challenge such applications in the courts if necessary. This will particularly be the case where account holders are aged 40 and above and are claiming non-domiciled status for the first time. Richard Murphy, director of Tax Research, said this estimate of £4.3 billion was based on an assumption that 20 per cent of non-domiciliaries would leave the UK. He has suggested introducing a system in which individuals are taxed on their worldwide income, much like that in the US, to replace the domicile rules. Mr Murphy said such a “passport” system would work in conjunction with residence rules. "You can use the current residence rules to determine who should pay tax here. If they spend more than 183 days in any tax year or more than 90 days a year over a four-year rolling period in the UK, they would pay tax on their worldwide wealth in the UK," he said.