IHTM23206 | Special valuation matters: related property
From HM Revenue & Customs · Inheritance Tax Manual
Where the related property () provisions under ) apply to an interest in property which needs to be valued, when completing VOA 1 or VOA 2 you must indicate clearly in the appropriate part of the joint property box
that the related property provisions apply,
and
the share to be valued (for example if the property is owned jointly by the deceased and their spouse or civil partner () you should indicate that the share to be valued is the entirety)