what type of income is neing taxed by Wisconsin.
only wages fall under the reciprocity agreements. Other income sourced to Wisconsin is taxed by both states but you get a credit on the Illinois return. Does box 15 of the W-2 show WI rather than IL. if so it seems your employer withheld for Wisconsin and not Illinois. thus you would have to file a WI return to get your taxes back and then owe IL
it's best to do the nonresident state first