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Moved from Illinois to Colorado Mid-Year: Which State Tax Returns Do You File?

Two part-year returnsBoth states claim the income

Answer

Illinois for the first part of the year, Colorado for the rest. Each state's part-year return reports the income received during that state's residency period and prorates the standard deduction, exemptions and credits accordingly. Keep evidence of the date you actually changed domicile.

Last verified

A mid-year move splits the tax year in two, and each state taxes its own half. That is a residency question, so the machinery that governs commuters — reciprocity agreements, convenience rules, nonresident withholding — is beside the point here.

What you file

  1. 1Part-year return · IllinoisForm IL-1040 with Schedule NR

    File a Illinois part-year return covering the months you lived in Illinois. A part-year resident of Illinois reports the income received while a Illinois resident, plus any Illinois-source income received during the rest of the year, and prorates the deductions and credits to the residency period.

  2. 2Part-year return · ColoradoForm DR 0104 with Schedule DR 0104PN

    File a Colorado part-year return covering the months you lived in Colorado. A part-year resident of Colorado reports the income received while a Colorado resident, plus any Colorado-source income received during the rest of the year, and prorates the deductions and credits to the residency period.

The two states, side by side

 IllinoisColorado
Taxes wagesYes — flatYes — flat
Reciprocity partners4 (Form IL-W-5-NR)None
Convenience ruleNoNo
Nonresident returnForm IL-1040 with Schedule NRForm DR 0104 with Schedule DR 0104PN
Part-year returnForm IL-1040 with Schedule NRForm DR 0104 with Schedule DR 0104PN
Credit for other-state taxSchedule CRForm DR 0104CR
Nonresident safe harbour30 daysNone published
Local income taxNoYes
Revenue departmentIllinois Department of RevenueColorado Department of Revenue — Taxation Division
Last verified

The other direction

Reversing the commute does not always reverse the answer. Living in Colorado and working in Illinois gives:Two part-year returns.

Colorado to Illinois →

Same two states, different situation

The withholding answer turns on how you are paid and where the work happens, not only on which two states are involved.

Other Illinois pairs

Questions people actually ask

I moved from Illinois to Colorado mid-year. Do I have to file in both states?

Illinois for the first part of the year, Colorado for the rest. Each state's part-year return reports the income received during that state's residency period and prorates the standard deduction, exemptions and credits accordingly. Keep evidence of the date you actually changed domicile.

How do I split my income between Illinois and Colorado?

By when you received it, measured against the date your domicile actually changed. Income received while you were a Illinois resident belongs on the Illinois return and income received afterwards on the Colorado return, with each state prorating your deductions, exemptions and credits to its own part of the year. Keep evidence of the move date — a lease, a closing statement, a licence issue date.

How current is this?

The Illinois and Colorado rules on this page were last checked against Illinois Department of Revenue and Colorado Department of Revenue — Taxation Division on 2026-08-07. We re-check the full grid every December after state legislative sessions close, and re-check the convenience-of-the-employer states quarterly because that is where the rules move fastest.

Sources

Every fact above comes from the revenue department that publishes the rule. We do not cite secondary summaries, and we do not restate a figure we could not find at source.