If you're married, you have only two filing options when it comes to your taxes: file a joint return with the person you're legally married to, or use the married filing separately status. The Internal Revenue Service lets you pick who you get married to, but once you tie the knot, you can't choose to file a joint tax return with a different person.
To file a joint return with anyone, you must be considered married to that person on the last date of the calendar year. Obviously, you're considered married if you're married and living together as a couple, or if you're legally considered married under common law. But, you're also considered married if you're living apart but not legally separated or divorced, if your divorce decree isn't final. So, even if you're planning on getting divorced so you can marry someone else, you can't file your taxes with that person yet.
Mark Kennan is a writer based in the Kansas City area, specializing in personal finance and business topics. He has been writing since 2009 and has been published by "Quicken," "TurboTax," and "The Motley Fool."