Where joint tenants hold land none owns a fractional share.
They all own the whole. When a joint tenant dies nothing passes to
his personal representatives as part of his estate. The land is
owned by the surviving tenant(s).
For CGT purposes, when the property is sold, each tenant is entitled to an equal share of the proceeds (CG70520 – CG70526).
It is possible to sever a joint tenancy and create a tenancy in common.
