IHTM15045 | The extent of the share (England, Wales and Northern Ireland): procedure where the property produces income but the deceased takes a different share to their supposed share of the property
From HM Revenue & Customs · Inheritance Tax Manual
This guidance applies where
property subject to a joint tenancy () produced income at any time after the joint ownership began, and
a joint owner enjoyed a share of income that was different from theproportion they could have obtained if they had severed () the joint tenancy
In this situation, the inference is that, whether or not the property passed by survivorship
it was not held in true joint tenancy, but
it was held under a parol trust (a trust, usually oral, not evidenced by a deed)
If the beneficial interests under that parol trust were such that the property could be treated as settled, you should consider applying the settled property () charging provisions. Such cases are likely to be rare, so you should consult Technical before claiming tax under those provisions.