IHTM30451 | Determination of questions on previous view of the law: scope of IHTA84/S255
From HM Revenue & Customs · Inheritance Tax Manual
In view of IHTA84/S255, where an assessment
you have to determine whether the assessment is correct by reference to the same view of the law. You cannot reopen the assessment because it appears from ‘a subsequent legal decision or otherwise’ that the view of the law was or may have been wrong.
We treat ‘a subsequent legal decision or otherwise’ as applying where the former view of the law is subsequently either
shown by judicial decision to be erroneous, or
is changed on the instructions of HMRC.