No, you may not subtract your out-of-state income. However, if you are filing as a resident or a part-year resident, you may be allowed to take a credit against Illinois Income Tax for income tax you paid to another state. See the
instructions for Form IL-1040, Line 15, and
Schedule CR, Credit for Tax Paid to Other States.
If you have additional inquiries, you may submit them to the Questions, Comments, or Request form.