1099 Contractor in Connecticut with a Idaho Client: Where Do You File?
Answer
Two possible returns, one certainty. The certainty is Connecticut, which taxes residents on all self-employment income and expects quarterly estimated payments. The possibility is Idaho, which taxes nonresidents on services actually performed inside the state — invoices sent there do not count.
Last verified
The client's location is the wrong thing to track. What matters is where you were sitting when you did the work — which is why a contractor's exposure to Idaho is measured in days on the ground rather than in invoices sent.
Idaho publishes no de minimis day count or dollar floor for nonresidents. Any Idaho-source wage income above the state's general filing threshold requires a nonresident return, and that threshold is reset each year — check the current figure on the Idaho State Tax Commission nonresident instructions before filing.
What you file
- 1Quarterly estimated payments · Connecticut
Make quarterly estimated payments to Connecticut Department of Revenue Services on your full self-employment income — nothing is withheld from a 1099.
- 2Nonresident return · IdahoForm 43
File a Idaho nonresident return only if you performed services inside Idaho. Idaho publishes no de minimis day count or dollar floor for nonresidents. Any Idaho-source wage income above the state's general filing threshold requires a nonresident return, and that threshold is reset each year — check the current figure on the Idaho State Tax Commission nonresident instructions before filing.
- 3Resident return · ConnecticutSchedule 2 (Form CT-1040)
File the Connecticut resident return last and claim the credit for any tax paid to Idaho.
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 |
| 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:Home state, plus the client state if you work there.
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
- Moved mid-year: Connecticut → IdahoTwo part-year returns
Other Connecticut pairs
Questions people actually ask
I live in Connecticut and my client is in Idaho. Do I have to file a Idaho tax return?
Two possible returns, one certainty. The certainty is Connecticut, which taxes residents on all self-employment income and expects quarterly estimated payments. The possibility is Idaho, which taxes nonresidents on services actually performed inside the state — invoices sent there do not count.
Do reciprocity agreements help a 1099 contractor?
No. Every state reciprocity agreement in the country is an arrangement about wage withholding between two revenue departments, and a 1099 has no withholding to switch off. Whether Connecticut and Idaho hold an agreement makes no difference to a self-employed filer — sourcing rules decide the answer instead.
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