Based on my calculations, the state tax liability that TurboTax calculated is about the same that I have already payed IL according to box 17 on my W-2. After I pay the $59 for the state return, what happens when I submit with the incorrectly overstated tax liability that they have calculated?
Don't submit an incorrect tax return. If it looks like you owe an amount of tax you already paid, double-check your numbers before submitting. You may have duplicated your income or maybe you forgot to enter the amounts from Box 17 into TurboTax. Search for W-2 and use the Jump to W-2 link to go to your W-2 summary. Is your W-2 only listed once? Delete one of them if you entered it twice. Click EDIT next to your W-2 and review all of the numbers you entered. Make sure all of the state boxes are entered correctly. Print or view your state return to ensure everything is correct. You should see your tax liability on Line 23/24 of your IL tax return. Your withholding is applied on Line 25.