IHTM14624 | Lifetime transfers: specific lifetime reliefs: fall in value relief: conditions for relief
From HM Revenue & Customs · Inheritance Tax Manual
All the following conditions must be satisfied before you can allow any relief
The value transferred by the failed potentially exempt transfer (IHTM04057) or chargeable transfer must be wholly or partly attributable to property which either
The market value (IHTM14626) of the transferred property at the time of the transfer must exceed its market value at the date of death or sale.
A claim in writing must be made by a person liable to pay the tax, or additional tax (IHTM14571), within 4 years of the date of the donor’s death, IHTA/S131(2ZA).