IHTM30455 - Determination of questions on previous view of the law: delay by HMRC

Where IHTA84/S255 does not otherwise prevent calculations being revised in favour of HMRC__ after a change in practice, you should consider whether any undue delay by HMRC may have contributed to the case being settled after, rather than before, the change in practice. The instructions on reopening IHT liabilities (IHTM30412) will be applicable. If it seems that this may be so, you should refer the case to your manager to decide whether in the circumstances we should treat IHTA84/S255 as applying to prevent us from claiming additional tax.