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. if you were in a civil union, you and your civil union partner must file with Illinois using either the "married filing jointly" or "married filing separately" filing status.
Since a civil union couple is not allowed to file a federal return using a married filing status:
- If you and your partner choose to file a joint Illinois return, you must recompute your adjusted gross income as if you had filed a federal married filing jointly return.
- If you and your partner choose to file separate Illinois returns, you must recompute your adjusted gross income as if you had both filed federal married filing separately returns.
Complete your federal "as-if-married" return(s), including all schedules and attachments, applying all the federal rules for the married filing status you choose. Enter the federal "as-if-married" return information where Illinois requires federal information. Do not file your federal "as-if-married" return(s) with the IRS. If you did not file your original return as married, you must correct that error by filing Form IL-1040-X using a married filing status, even if the extended due date has passed.