Non-doms need to be extra vigilant when filing their tax returns before the January deadline, or risk a ‘disproportionately high' bill from the taxman, warns KPMG.
By 31 January, UK resident non-dom taxpayers have to notify HM Revenue & Customs (HMRC) of any tax for which they are liable.
They will have to decide whether to claim the remittance basis - keeping their offshore profits outside the UK tax net - or to pay UK tax on their worldwide income or gains.
For those living in the UK for seven or more years, they also have to pay the £30,000 fee if they want to use the remittance basis.
The revised tax rules for non-dom taxpayers living in the UK have been in place since 2008, but this is the first time the rules will really have an impact, according to KPMG.
David Kilshaw, head of private client advisory at KPMG UK, says: "This could be the most important tax return of their lives. There are many rules and potential traps, so non-dom taxpayers need to consider their returns very closely. One small slip could trigger a disproportionately high tax bill."
He says the way HMRC deals with these returns could also have a significant impact on the future of the UK as a financial centre.
"These are complex new rules, which taxpayers and HMRC alike are struggling with. HMRC can be expected to enquire into a large number of returns to make sure they are correct, and rightly so.
"But it is also to be hoped their approach with be sympathetic and understanding. If HMRC were to be unduly aggressive or suspicious in their dealing with the returns filed, this could be the straw which causes many non-doms to leave the UK."
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