Illinois Car Sales Tax Calculator

Illinois uses two different systems for vehicle purchases. A registered Illinois dealer reports vehicle tax through ST-556 using a vehicle-specific Auto Rate and supported location adjustments. An ordinary private-party purchase uses the fixed RUT-50 vehicle use tax tables instead of multiplying the price by the normal 6.25% state rate.

The calculator switches engines based on the transaction type so an Illinois used car sale is not forced into the wrong tax method.

A supported dealer sale begins with the Auto Rate for the dealer's registered standard business location. The engine uses the motor-vehicle fields in IDOR's August 1, 2026 machine-readable file rather than a general-merchandise combined rate.

The taxable selling price can include the vehicle, accessories, freight, labor, dealer preparation, documentary charges, and a manufacturer or other reimbursed rebate. A verified retailer-funded discount that is not reimbursed can reduce the selling price.

Qualifying trade-in value and loan payoff

The full qualifying trade-in value can reduce the taxable amount for a supported dealer transaction. The old $10,000 limit no longer applies. A loan payoff changes positive or negative trade equity, but it does not reduce the Illinois trade-in sales-tax credit.

Illinois vehicle tax can depend on both the dealer's standard business location and the purchaser's registration address. The engine isolates the ST-556 Chicago rule for a purchaser registered inside Chicago when the dealer is in Cook, DuPage, Kane, Lake, McHenry, or Will County.

It also applies the supported positive NITA or Metro-East district difference when the purchaser's registration location requires it. When a Metro-East override cannot be safely determined from county alone, the calculator asks for district confirmation instead of substituting a generic rate.

St. Clair Metro-East source note

The current machine-readable file contains a conflicting MED fee field. The transaction-specific ST-556 instructions separately direct a 0.5% fee, capped at $20, for a supported business location in the Metro-East portion of St. Clair County. The verified engine follows that transaction instruction and does not change the Auto high/low fields.

An ordinary private-party purchase does not use purchase price multiplied by 6.25%. For a value under $15,000, the 2026 RUT-50 state amount is determined by vehicle age. At $15,000 or more, the state amount comes from fixed purchase-price or fair-market-value brackets.

RUT-50 allows no trade-in deduction. The buyer must enter the purchase price or fair market value required by the official rule; CarBuyerKit does not invent a value.

Chicago and Cook County private-party taxes

RUT-6 adds age-based Chicago and Cook County amounts when the address on the title or registration application requires them. A Chicago address in Cook County can receive both additions.