Updated October 24, 2026. Quick answer: This guide walks the lines of the Illinois IL-1040 and its Schedule M that a retiree most often reads: income, base income, the exemption allowance, two credits and the Schedule M subtractions. Each line has its own page that quotes the Illinois Department of Revenue’s 2025 instructions for it. The retirement income subtraction on line 5 already has its own page: IL-1040 line 5 retirement income subtraction.
The lines covered
Pick the line you are stuck on. Each page quotes the 2025 instructions for that line, says who it applies to and shows where the result goes next.
| Line | Page | Where it sits |
|---|---|---|
| IL-1040 line 1 | Federal adjusted gross income | IL-1040 income |
| IL-1040 line 2 | Federally tax-exempt income | IL-1040 income |
| IL-1040 line 3 | Other additions | IL-1040 income |
| IL-1040 line 7 | Other subtractions | IL-1040 base income |
| IL-1040 line 9 | Illinois base income | IL-1040 base income |
| IL-1040 line 10 | Exemption allowance | IL-1040 exemptions |
| IL-1040 line 15 | Income tax paid to another state | IL-1040 credits |
| IL-1040 line 16 | Property tax and K-12 education credits | IL-1040 credits |
| Schedule M line 13 | College savings contributions | Schedule M subtractions |
| Schedule M line 21 | Military pay earned | Schedule M subtractions |
| Schedule M line 22 | U.S. Treasury and agency interest | Schedule M subtractions |
| Schedule M line 25 | Recovery of items previously deducted | Schedule M subtractions |
| Schedule M line 27 | Life insurance, endowment and annuity benefits | Schedule M subtractions |
| Schedule M line 37 | Railroad sick pay and unemployment | Schedule M subtractions |
| Schedule M line 42 | Total subtractions | Schedule M subtractions |
How the base income lines connect
The form’s own labels set out the order. Step 3 closes with “Illinois base income. Subtract Line 8 from Line 4.” and the subtractions total just above it reads “Add Lines 5, 6, and 7. This is the total of your subtractions.”
For the state-level picture of how Illinois treats retirement income, see Illinois retirement taxes and whether Illinois taxes pensions.
Edition and line numbers
These pages read the 2025 Form IL-1040 Instructions, the 2025 Schedule M Instructions and the forms themselves from the Illinois Department of Revenue, the current files served on 2026-10-24. Check the edition printed on your own form and use that edition’s line numbers.
Related: Illinois 401(k) and IRA withdrawals, Form 1040 line 5a and 5b, and Form 1040 line 4a and 4b.
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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.