Incorrect Calculation of Illinois Taxable Income

[Very Angry]

 am using the Desktop TurboTax 2025.

TurboTax incorrectly computes my benefits deduction from my Federal AGI for my Illinois income tax.  All Social Security benefits, pension benefits, and IRA/401k are exempt from Illinois Taxation.

Federal Income tax taxes 85% of my Social Security. In computing my benefit deduction from Illinois taxable income, TurboTax adds the TAXED amount rather than the total Social Security benefit. This results in Illinois taxing 15% of my Social Security benefit in the TurboTax computation.

I went back to 2022, 2023, and 2024 returns. In each case, I have been taxed incorrectly on 15% of my Social Security Benefit.

[VolvoGirl]

The 15% is not taxed by federal so it doesn't show up on the state return to start with.  Only the 85% taxable amount needs to be subtracted from state.   

[Very Angry]

Yes, I had my wishful thinking cap on, thinking that Illinois didn't tax my Social Security, but they do.

[VolvoGirl]

Illinois does NOT tax Social Security.  Are you still confused?  

States that tax Social Security. Colorado, Connecticut, Minnesota, Montana, New Mexico, Rhode Island, Utah, Vermont, and West Virginia (not sure about WV).

[AnnetteB6]

Take a look at your Form 1040 line 6b which shows the amount of your Social Security that is taxed on your Federal return.  Also look at Form 1040 line 11a which is your Federal Adjusted Gross Income (AGI).

Now take a look at your IL Form IL-1040 line 1.  This should be the same number as Form 1040 line 11a, your AGI.  Since this number comes from your Federal return, it include the amount of taxable Social Security shown on line 6b.  

Next, look at IL Form IL-1040 line 5 which should be the same number as Form 1040 line 6b, taxable Social Security.  This line 5 is then combined with lines 6 and 7 and the total is on line 8.  Then, see the instruction for IL Form IL-1040 line 9 -- the amount on line 8 is subtracted from your Illinois income, therefore removing the taxable Social Security from the equation before your Illinois tax is calculated.  

@Very Angry