This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

Inheritance Tax Manual

Estate Duty surviving spouse exemption: benefits under intestacy (England & Wales)

If a surviving spouse has disclaimed the statutory sum to which they were entitled under the intestacy of the first spouse to die, without also disclaiming any life interest (or in Northern Ireland, their absolute interest) in the residuary estate to which they were entitled to, you should not refuse exemption on the grounds of competent to dispose (IHTM04457) in respect of the portion of the residuary estate attributable to the disclaimed sum.

The surviving spouse of an intestate has the statutory right to elect to have the capital value of their life interest under the intestacy paid to them. This right, if not exercised, is not regarded as making them competent to dispose of any of the settled property.