The State of Illinois allows a subtraction from income for certain military pay earned, which is claimed on IL Schedule M Other Additions and Subtractions for Individuals.

Per Instructions for the Schedule M, on page 3:

Line 21 - Military pay earned

Enter the amount of military pay that you received from the U.S. Armed Forces or the National Guard of any state, or that you received as a dual status military technician.

You may not subtract the following:

• combat pay that is not included in your federal adjusted gross income, Form IL-1040, Line 1
• pay you received
  • under the Voluntary Separation Incentive,
  • from the military as a civilian,
  • under the Ready Reserve Mobilization Income Insurance Program,
  • for duty as an officer in the Public Health Service

For more information, see Publication 102, Illinois Filing Requirements for Military Personnel.

Attach Form W-2 showing your military pay. If you report dual status on Line 21, you must attach both Form W-2 and SF-50, Standard Form 50 (Notification of Personnel Action).

To enter this in TaxAct:

1. From within your TaxAct return (Online or Desktop), click State, then click Illinois (or IL). On smaller devices, click in the upper left-hand corner, then click State.
2. Click Income in the Illinois Quick Q&A Topics menu to expand, then click Subtractions.
3. Continue with the interview process to enter all of the appropriate information.
4. On the screen titled Illinois - Other Subtractions From Income, click Yes.
5. On the screen titled Illinois - Miscellaneous Subtractions, enter the Military pay earned (income reported on W-2) amount, then click Continue.

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.