In a briefing note published last week HMRC specify that they will henceforth challenge domicile only where " there is a significant risk of loss of UK tax."
According to HMRC, they will take a more risk based approach for inheritance tax cases. Revenue & Customs Brief 34/10 states:
"The significance of the risk will be assessed by HMRC using a wide range of factors. The factors will depend very much on the individual case but will include, for example: a review of the information available to HMRC about the individual on HMRC databases whether there is a significant amount of tax (all taxes and duties not just Inheritance Tax) at risk
HMRC does not consider it appropriate to state an amount of tax that would be considered significant, as the amount of tax at stake is only one factor. "
The new policy takes effect for dispositions after 24 August 2010. The full text of Revenue & Customs Brief 34/10 can be found here.