The Internal Revenue Service does allow some couples who are not conventionally married to file joint tax returns. However, choosing to file a joint return is a relatively permanent decision that extends beyond the current tax year, and it is a decision that should not be made lightly. If you and your girlfriend qualify to file jointly, you’ll want to consider the potential longevity of your relationship and calculate the benefits and risks associated with submitting a joint return.
The IRS requires that you are considered married in order to file a joint tax return. However, since the IRS is a federal entity, it does not govern how each state independently defines marriage. If you meet state definitions, you and your girlfriend may file a joint return if, on the last day of the tax year, you live together as husband and wife.
Common Law Rules
For the purpose of defining relationships not unionized in a legal marriage proceeding, the IRS recognizes common law rules established by the state where you and your girlfriend live. This means that even if you began your relationship in a state that does not recognize common law unions, but live in a state that does when you file your tax return, the IRS will allow your marriage based on the rules of your current residential state.
Preparing a joint return is not a light decision. After you file a joint return, the IRS does not allow you to change the filing status for the year after the due date for the return has passed, which is April 15. If you later find that filing jointly was inappropriate, you can only change a joint filing status on a filed return if you obtain a court-ordered annulment. An annulment differs from a divorce in that instead of dissolving a valid marriage, it asserts that a valid marriage never existed. If you obtain an annulment, you must file an amended return to make changes to your filing status for the year you filed jointly.
Filing Single Later
After you file a joint return with your girlfriend, you have informed the IRS that you are married. Going forward, you may only choose to file as married filing jointly or married filing separately. If you and your girlfriend split up, you’ll need to obtain a court-ordered separation or divorce to file single again. However, if you have split up and have qualifying dependents, you qualify to use the unmarried head of household status if you and your girlfriend have lived apart for the last six months of the year.