Moved from Idaho to Illinois Mid-Year: Which State Tax Returns Do You File?
Answer
Both states want a return, but neither taxes the whole year. Moving from Idaho to Illinois splits the tax year at the date your residency changed: a Idaho part-year return covers everything before it, a Illinois part-year return everything after. Income is assigned by when it was received.
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
- 1Part-year return · IdahoForm 43 (part-year resident)
File a Idaho part-year return covering the months you lived in Idaho. A part-year resident of Idaho reports the income received while a Idaho resident, plus any Idaho-source income received during the rest of the year, and prorates the deductions and credits to the residency period.
- 2Part-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.
The two states, side by side
| Idaho | Illinois | |
|---|---|---|
| Taxes wages | Yes — flat | Yes — flat |
| Reciprocity partners | None | 4 (Form IL-W-5-NR) |
| Convenience rule | No | No |
| Nonresident return | Form 43 | Form IL-1040 with Schedule NR |
| Part-year return | Form 43 (part-year resident) | Form IL-1040 with Schedule NR |
| Credit for other-state tax | Form 39NR | Schedule CR |
| Nonresident safe harbour | None published | 30 days |
| Local income tax | No | No |
| Revenue department | Idaho State Tax Commission | Illinois Department of Revenue |
| Last verified |
The other direction
Reversing the commute does not always reverse the answer. Living in Illinois and working in Idaho gives:Two part-year returns.
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.
- W-2 commuter: Idaho → IllinoisBoth states — credit offsets the double tax
- Remote worker: Idaho → IllinoisHome state only
- 1099 contractor: Idaho → IllinoisHome state, plus the client state if you work there
Other Idaho pairs
Questions people actually ask
I moved from Idaho to Illinois mid-year. Do I have to file in both states?
Both states want a return, but neither taxes the whole year. Moving from Idaho to Illinois splits the tax year at the date your residency changed: a Idaho part-year return covers everything before it, a Illinois part-year return everything after. Income is assigned by when it was received.
How do I split my income between Idaho and Illinois?
By when you received it, measured against the date your domicile actually changed. Income received while you were a Idaho resident belongs on the Idaho return and income received afterwards on the Illinois 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 Idaho and Illinois rules on this page were last checked against Idaho State Tax Commission and Illinois Department of Revenue 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.
- Idaho State Tax Commission — individual income taxaccessed 2026-08-07
- Illinois Department of Revenue — individual income taxaccessed 2026-08-07