For federal tax purposes, the terms “spouse,” “husband,” and “wife” includes individuals of the same sex who were lawfully married under the laws of a state whose laws authorize the marriage of two individuals of the same sex and who remain married. Also, the Service will recognize a marriage of individuals of the same sex that was validly created under the laws of the state of celebration even if the married couple resides in a state that does not recognize the validity of same-sex marriages.
However, the terms “spouse,” “husband and wife,” “husband,” and “wife” do not include individuals (whether of the opposite sex or the same sex) who have entered into a registered domestic partnership, civil union, or other similar formal relationship recognized under state law that is not denominated as a marriage under the laws of that state, and the term “marriage” does not include such formal relationships.
All property that is included in the gross estate and passes to the surviving spouse is eligible for the marital deduction. The property must pass “outright.” In some cases, certain life estates also qualify for the marital deduction.