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1099 Contractor in South Carolina with a Illinois Client: Where Do You File?

Home state, plus the client state if you work thereNo withholding — 1099

Answer

South Carolina taxes all of it; Illinois taxes only what you earn on its soil. Nothing is withheld from a 1099, so you pay South Carolina quarterly. A Illinois client alone creates no Illinois filing obligation — performing services inside Illinois does, and South Carolina then credits that tax.

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 Illinois is measured in days on the ground rather than in invoices sent.

Illinois allows a 30-day safe harbour before the obligation attaches. Illinois does not require an employer to withhold from a nonresident who works in Illinois for 30 or fewer days in the year. The day count is a withholding safe harbour; a nonresident who exceeds it owes Illinois tax on the Illinois-source wages.

What you file

  1. 1Quarterly estimated payments · South Carolina

    Make quarterly estimated payments to South Carolina Department of Revenue on your full self-employment income — nothing is withheld from a 1099.

  2. 2Nonresident return · IllinoisForm IL-1040 with Schedule NR

    File a Illinois nonresident return only if you performed services inside Illinois. Illinois does not require an employer to withhold from a nonresident who works in Illinois for 30 or fewer days in the year. The day count is a withholding safe harbour; a nonresident who exceeds it owes Illinois tax on the Illinois-source wages.

  3. 3Resident return · South CarolinaForm SC1040TC

    File the South Carolina resident return last and claim the credit for any tax paid to Illinois.

The two states, side by side

 South CarolinaIllinois
Taxes wagesYes — graduatedYes — flat
Reciprocity partnersNone4 (Form IL-W-5-NR)
Convenience ruleNoNo
Nonresident returnForm SC1040 with Schedule NRForm IL-1040 with Schedule NR
Credit for other-state taxForm SC1040TCSchedule CR
Nonresident safe harbourNone published30 days
Local income taxNoNo
Revenue departmentSouth Carolina Department of RevenueIllinois Department of Revenue
Last verified

The other direction

Reversing the commute does not always reverse the answer. Living in Illinois and working in South Carolina gives:Home state, plus the client state if you work there.

Illinois to South Carolina →

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 South Carolina pairs

Questions people actually ask

I live in South Carolina and my client is in Illinois. Do I have to file a Illinois tax return?

South Carolina taxes all of it; Illinois taxes only what you earn on its soil. Nothing is withheld from a 1099, so you pay South Carolina quarterly. A Illinois client alone creates no Illinois filing obligation — performing services inside Illinois does, and South Carolina then credits that tax.

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 South Carolina and Illinois hold an agreement makes no difference to a self-employed filer — sourcing rules decide the answer instead.

How current is this?

The South Carolina and Illinois rules on this page were last checked against South Carolina Department of Revenue 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.