I live in the same apartment with my girlfriend and am planning to marry her. Can I file a joint return with my girlfriend?

A couple can only file a joint return if they are treated as married under United States law. There may be situations where a couple is considered married without having gone through the official ceremony. An attorney who specializes in these matters should be consulted if there is a questionable situation.

Example: A couple has been living together for two years and gets married in February 2005. A month after the wedding the newlyweds would like to file their 2004 tax return jointly. Because they were not married at the end of 2004, they still have a single filing status and should file their tax returns separately.