SolvedIHTM30154 | Due date for payment: relevant property trusts
From HM Revenue & Customs · Inheritance Tax Manual
Where the charge to tax under Chapter 3 Part 3 IHTA84 arises on or after 6 April 2014, the tax is payable six months after the end of the month in which the chargeable event occurred, IHTA84/S226(3C).
Where the tax charged under Chapter III Part III IHTA 1984 arose before 6 April 2014, the tax is payable
for chargeable events after 5 April and before 1 October, on 30 April in the following year
for chargeable events after 30 September and before 6 April, six months after the end of the month in which the chargeable event took place.
There are two exceptions to this general rule