IHTM35212 | Provisions relating to Legitim: the basic rule in s.147
From HM Revenue & Customs · Inheritance Tax Manual
Under the basic rule in , you should charge tax as if legitim () has been claimed. This means that you should restrict spouse or civil partner exemption () () by allowing for the legitim entitlement in full. However, if the person(s) entitled to claim legitim renounce () their claim either
before attaining 18, or
within two years of attaining 18, or such longer period as the Board may allow
the amount of spouse or civil partner exemption can be revised accordingly. The usual time limit for repaying tax in is removed, , and you should add the interest supplement () to the repayment in the usual way.
You should refer any case where a period longer than two years is proposed to Technical.
However, if the executors so wish they can elect () under that the provisions of should apply to the estate.