Moved from Connecticut to Illinois Mid-Year: Which State Tax Returns Do You File?
Answer
Two returns, split at the move date. Connecticut and Illinois both tax residents, so each takes the portion of the year you were one. This is a residency question rather than a sourcing question — reciprocity agreements and convenience rules have nothing to do with it.
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 · ConnecticutForm CT-1040NR/PY
File a Connecticut part-year return covering the months you lived in Connecticut. A part-year resident of Connecticut reports the income received while a Connecticut resident, plus any Connecticut-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
| Connecticut | Illinois | |
|---|---|---|
| Taxes wages | Yes — graduated | Yes — flat |
| Reciprocity partners | None | 4 (Form IL-W-5-NR) |
| Convenience rule | Only against convenience-rule states | No |
| Nonresident return | Form CT-1040NR/PY | Form IL-1040 with Schedule NR |
| Part-year return | Form CT-1040NR/PY | Form IL-1040 with Schedule NR |
| Credit for other-state tax | Schedule 2 (Form CT-1040) | Schedule CR |
| Nonresident safe harbour | None published | 30 days |
| Local income tax | No | No |
| Revenue department | Connecticut Department of Revenue Services | Illinois Department of Revenue |
| Last verified |
The other direction
Reversing the commute does not always reverse the answer. Living in Illinois and working in Connecticut 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: Connecticut → IllinoisBoth states — credit offsets the double tax
- Remote worker: Connecticut → IllinoisHome state only
- 1099 contractor: Connecticut → IllinoisHome state, plus the client state if you work there
Other Connecticut pairs
Questions people actually ask
I moved from Connecticut to Illinois mid-year. Do I have to file in both states?
Two returns, split at the move date. Connecticut and Illinois both tax residents, so each takes the portion of the year you were one. This is a residency question rather than a sourcing question — reciprocity agreements and convenience rules have nothing to do with it.
How do I split my income between Connecticut and Illinois?
By when you received it, measured against the date your domicile actually changed. Income received while you were a Connecticut resident belongs on the Connecticut 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 Connecticut and Illinois rules on this page were last checked against Connecticut Department of Revenue Services 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.
- Connecticut Department of Revenue Services — individual income taxaccessed 2026-08-07
- Illinois Department of Revenue — individual income taxaccessed 2026-08-07