You can claim the Single filing status on your tax return if you are unmarried  on the last day of the year. This includes people who if on the last day of the year, are unmarried or legally separated from their spouse under a divorce or separate maintenance decree, and do not qualify for another filing status.

Unmarried taxpayers who can claim a dependent should check to see if they qualify for the Head of Household filing status. Head of Household status will provide more tax benefits than claiming single.

 (IRS Publication 501, "Single").

 

State law governs whether you are married or legally separated under a divorce or separate maintenance decree.

 

Married taxpayers can choose between filing a joint tax return or a separate tax return. The Married Filing Separately filing status provides fewer tax benefits than filing joint returns, If you are unsure of the legality of your spouses income or income statements, it is advised to file separately to reduce your liability from the other spouses actions.

 

Domestic Partners are Considered Unmarried

The Federal Defense of Marriage Act of 1996 defined marriage as, a legal union between one man and one woman as husband and wife. The word spouse refers only to a person of the opposite sex who is a husband or a wife.

Some states, such as California, are requiring domestic partners to file tax returns as if they were married. Domestic partners should consult with an experienced tax professional for advice on filing their federal and state tax returns.