Updated October 24, 2026. Quick answer: Line 1 of the 2025 Illinois IL-1040 starts the income step. The instructions open with “Enter the adjusted gross income from your federal return.” It is the first of the figures that line 4 adds together.
What this line asks
On the form the line reads “Federal adjusted gross income from your federal Form 1040 or 1040-SR, Line 11a.” The instructions put the same request this way: “Enter the adjusted gross income from your federal return.” For how the federal figure is built, see Form 1040 lines 9, 10, 11 and AGI and Form 1040 line 1a.
Who it applies to
Line 1 sits at the top of Step 2, which the form titles “Step 2: Income”. The one condition the instructions print for getting the figure is this: “If you are not required to file a federal income tax return, use a federal Form 1040 as a worksheet to determine your adjusted gross income.”
Retirees whose pension, IRA or annuity payments are part of that federal total will see them here first; the Illinois treatment of that income is covered in Illinois retirement taxes and whether Illinois taxes pensions.
What the instructions say to enter
| Step | What the instructions say |
|---|---|
| Start with the federal figure | “Enter the adjusted gross income from your federal return.” |
| If you did not file a federal return | “If you are not required to file a federal income tax return, use a federal Form 1040 as a worksheet to determine your adjusted gross income.” |
| Net operating loss this year | “If you have a federal NOL this year, you may enter a negative amount on Line 1.” |
| Carrybacks | “However, you must reduce the amount you enter on your 2025 Form IL-1040, Line 1, by any NOL that you carry back to prior years.” |
| Carryforwards | “Any amounts carried forward to future years should not be used to reduce IL-1040, Line 1.” |
| No double deduction | “Illinois does not allow you to deduct the same NOL twice.” |
The figures the line prints
The instructions for this line print no dollar amounts or percentages. The only year printed is in the sentence about carrybacks: “However, you must reduce the amount you enter on your 2025 Form IL-1040, Line 1, by any NOL that you carry back to prior years.”
Where the result goes next
The form’s next entries are line 2 and line 3, and then line 4: “Total income. Add Lines 1 through 3.” The step-by-step layout is on the Illinois IL-1040 line by line page.
Edition and line numbers
This page reads the 2025 Form IL-1040 Instructions from the Illinois Department of Revenue, the current file served on 2026-10-24. Check the edition printed on your own form and use that edition’s line numbers.
Common mistakes
- Using a net operating loss carried forward to a later year to reduce line 1. The instructions say “Any amounts carried forward to future years should not be used to reduce IL-1040, Line 1.”
- Taking the same loss twice. The instructions say “Illinois does not allow you to deduct the same NOL twice.”
- Skipping the carryback adjustment. The instructions say “However, you must reduce the amount you enter on your 2025 Form IL-1040, Line 1, by any NOL that you carry back to prior years.”
Related: Illinois retirement taxes, whether Illinois taxes pensions, Form 1040 lines 9, 10, 11 and AGI, and Form 1040 line 1a.
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Answer againSources
- 2025 Form IL-1040 Instructions, Illinois Department of Revenue: tax.illinois.gov
- 2025 Form IL-1040 Individual Income Tax Return, Illinois Department of Revenue: tax.illinois.gov
Read from the state revenue documents linked above on October 24, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer or the state revenue department is the right place to confirm anything consequential.