What a financed car actually costs out the door in Illinois — the sales tax this state really charges, whether it credits your trade-in, and what the payment does to what you can borrow for a house.
Trading a car in here reduces the amount sales tax is charged on, so you are taxed on the price less your trade-in allowance. That is the common rule, but it is not universal — a handful of states tax the full sticker price regardless, and the calculator below applies whichever rule is actually Illinois’s.
Illinois layers substantial local tax on the 6.25% state rate, and a vehicle is taxed at the rate for the relevant location rather than a flat statewide figure. IDOR's Vehicle Use Tax schedule puts Cook County at 7.25% (7.5% from 2026-08-01); DuPage, Kane, Lake, McHenry and Will at 7.0% (7.25% from 2026-08-01); and Madison and St. Clair at 6.5% inside the Metro East Transit District, 6.25% outside it. For dealer sales IDOR preprints a combined rate on the ST-556 reflecting home-rule tax at the dealer's location, and a dealer in Cook, DuPage, Kane, Lake, McHenry or Will selling to a buyer inside Chicago city limits must collect a further 1.25% Chicago Home Rule Use Tax. Treat 6.25% as a floor, not a typical rate.
Money factor, residual, and the payment — taxed by your state's actual method, since some states tax a lease's full value upfront instead of each payment.
Which dealer offer actually costs less over the life of the loan, and the rate at which they tie.
Income, savings, and debts in — max home price and qualification signal out.
A dealer offers 0% financing or $3,000 cash back. On a $38,000 car over 60 months the two cost exactly the same at 3.70% — and above that, the 0% wins by thousands.
Co-signing a $683-a-month car loan cuts the house payment you can qualify for by $683 — dollar for dollar. And if it defaults, you owe the whole balance, not half.
One number, in writing, itemised — and the scripts that get it. Every line a dealer can add, which of them are negotiable, and what your own state's tax rules do to the total.
One number, itemised, with the taxable amount working your state's trade-in rule live rather than leaving it to you to remember: four states with a sales tax credit nothing against a trade-in, and Ohio credits it against a new vehicle only. Checks a documentation fee against the nine statutory caps this site has confirmed, and is explicit that the other 41 states are unresearched rather than uncapped. Prices the F&I office as the optional extra it is, and adds the trade-in payoff back into the amount financed — because negative equity does not disappear when you trade the car, it moves into the new loan and accrues interest.