Like the standard nil rate band, any unused RNRB can be transferred between spouses and civil partners to be used when the survivor of them dies, regardless of when the first death occurred and whether or not the first deceased held a qualifying residential interest (that is, property ownership is not required by the first deceased). The only check that is required is whether the first deceased’s estate was over £2 million.
The transferable RNRB must be claimed by the personal representatives within two years from the end of the month in which the second death occurs.
The fact that a spouse may not have owned a residence does not preclude the surviving spouse on death claiming what is an unused RNRB on the part of the first spouse to die.