"U.S. Citizens and Resident Aliens Abroad - Head of Household
If you are a U.S. citizen married to a nonresident alien you may qualify to use the head of household tax rates. You are considered unmarried for head of household purposes if your spouse was a nonresident alien at any time during the year and you do not choose to treat your nonresident spouse as a resident alien. However, your spouse is not a qualifying person for head of household purposes. You must have another qualifying person and meet the other tests to be eligible to file as a head of household."