When a decedent dies, an estate tax will be due on the value of their estate that exceeds the unified credit for the year of death. Federal tax law provides for an unlimited marital deduction between married couples (not available to domestic partners and restrictions apply to non-US citizen spouses). This means that a decedent's property passing to his surviving spouse will not be subject to estate tax to the extent a marital deduction is claimed which can effectively defer payment of any estate tax until the death of the surviving spouse. However, any property from the decedent's estate for which the marital deduction is claimed will be included in the surviving spouse's estate and may be subject to estate tax if the surviving spouse still owns the property at her death. The marital deduction is also available to lifetime gifts between spouses.