Moved from Connecticut to Idaho Mid-Year: Which State Tax Returns Do You File?
Answer
Expect a part-year filing on each side. The point of a part-year return is that neither state taxes the whole year, so you are not double-taxed by default — but income received close to the move date has to be assigned carefully, and a lingering Connecticut source can still pull a nonresident filing along 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 · 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.
The two states, side by side
| Connecticut | Idaho | |
|---|---|---|
| Taxes wages | Yes — graduated | Yes — flat |
| Reciprocity partners | None | None |
| Convenience rule | Only against convenience-rule states | No |
| Nonresident return | Form CT-1040NR/PY | Form 43 |
| Part-year return | Form CT-1040NR/PY | Form 43 (part-year resident) |
| Credit for other-state tax | Schedule 2 (Form CT-1040) | Form 39NR |
| Nonresident safe harbour | None published | None published |
| Local income tax | No | No |
| Revenue department | Connecticut Department of Revenue Services | Idaho State Tax Commission |
| Last verified |
The other direction
Reversing the commute does not always reverse the answer. Living in Idaho 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 → IdahoBoth states — credit offsets the double tax
- Remote worker: Connecticut → IdahoHome state only
- 1099 contractor: Connecticut → IdahoHome state, plus the client state if you work there
Other Connecticut pairs
Questions people actually ask
I moved from Connecticut to Idaho mid-year. Do I have to file in both states?
Expect a part-year filing on each side. The point of a part-year return is that neither state taxes the whole year, so you are not double-taxed by default — but income received close to the move date has to be assigned carefully, and a lingering Connecticut source can still pull a nonresident filing along with it.
How do I split my income between Connecticut and Idaho?
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 Idaho 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 Idaho rules on this page were last checked against Connecticut Department of Revenue Services and Idaho State Tax Commission 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
- Idaho State Tax Commission — individual income taxaccessed 2026-08-07