Generally, the value of all joint tenancy property is included in the estate of the first joint tenant to die, except for the proportion the executor can prove was contributed to its acquisition by the surviving joint tenant and/or as a gift by a third party to the credit of the surviving joint tenant. If the surviving spouse and the decedent were the only joint tenants, only one-half of the value of the joint tenancy property will be included in the estate.
As result of the marital deduction, property held jointly by spouses with rights of survivorship does not trigger any estate tax in the estate of the first spouse to die. Technically, only one-half of the jointly held property would be included in the estate, and that one-half would be excluded by the marital deduction. The act similarly applies to tenancies by the entirety.