IRS Publication 17 — Your Federal Income Tax (Individuals)

explaining that your spouse is serving in a combat zone. For more information on special tax rules for persons who are serving in a combat zone, or who are in missing status as a result of serving in a combat zone, see Pub. 3.

Power of attorney. In order for you to sign a return for your spouse in any of these cases, you must attach to the return a power of attorney (POA) that authorizes you to sign for your spouse. You can use a POA that states that you have been granted authority to sign the return, or you can use Form 2848, Power of Attorney and Declaration of Representative. Part I of Form 2848 must state that you are granted authority to sign the return. Nonresident alien or dual-status alien. Generally, a married couple can’t file a joint return if either one is a nonresident alien at any time during the tax year. However, if one spouse was a nonresident alien or dual -status alien who was married to a U.S. citizen or resident alien at the end of the year, the spouses can choose to file a joint return. If you do file a joint return, you and your spouse are both treated as U.S. residents for the entire tax year. See chapter 1 of Pub. 519.