In general, most taxpayers should use the same filing status as on their federal return. However:
- If you are married, you filed a joint federal return, and you are an injured spouse (e.g., your spouse owes a liability, for which you are not responsible, to a government agency), you should file separate Illinois returns using the "married filing separately" filing status. If you file a joint Illinois return, we may take the entire refund to pay your spouse's liability. If you did not make this election on your original Form IL-1040, you may file Form IL-1040-X to make or revoke this election only if the extended due date of the return has not passed, and once the election is made it is irrevocable.
- If either you or your spouse is an Illinois resident and the other is a part-year resident or nonresident, and you elect to file a joint return, you will both be treated as residents. If you originally filed a joint return, but did not treat both yourself and your spouse as Illinois residents, you must correct that error by either filing a joint Form IL-1040-X treating yourselves as Illinois residents or by filing separate IL-1040-X forms, even if the extended due date has passed. If you file separate IL-1040-X forms, each spouse must list his or her own income separately even if one spouse did not have any Illinois income. Any spouse filing as a nonresident or part-year resident must also attach a completed Schedule NR.
- If you filed your federal return using the "married filing separately" filing status, you must file your Illinois return using the same filing status.