IHTM05013 | Requirement for a grant: HMRC's role
From HM Revenue & Customs · Inheritance Tax Manual
The personal representative (IHTM05012) (PR) may also be required to list all the assets and liabilities of the deceased person in an account, form IHT400 (IHTM10021). The PR is excused from having to submit an account form IHT400 where:
In cases where a form IHT400 is required it should be sent to us at the same time payment is made. Once we are sure that the tax has been paid, we will be able to issue either form IHT421 or, for estates in England and Wales from 17 January 2024, a letter with a unique code, to confirm we have received the IHT400 and any tax. The PR can then obtain the grant and deal with the administration of the estate.