The last twenty minutes

Put the advertised price and the out-the-door total side by side.

You should have an itemized sheet: vehicle price, sales tax, title, registration, and the documentary fee. Every one of those is a separate line with its own number, and the sum is what leaves your account. If the only figure anyone has said out loud so far is a monthly payment, stop here — a payment is an outcome of four variables and tells you nothing about any of them.

Check the vehicle price against what the car was advertised at. It should match exactly. If it doesn't, ask what the difference is and get the answer as a named line item rather than an explanation.

Read the Buyer's Guide, the window sticker, all of it.

Federal rules require dealers to display a Buyer's Guide on most used vehicles offered for sale, and its terms become part of your sales contract — it overrides anything in the contract that contradicts it. So the box that's checked on it matters: a warranty, with its duration and the percentage of parts and labor covered, or As Is, meaning the dealership takes on no responsibility for repairs after the sale.

New Jersey also has a used car lemon law with age and mileage thresholds of its own, and whether a particular car falls inside them is worth confirming rather than assuming in either direction. If a salesperson made a verbal promise about a repair, it belongs in writing here or on the contract — not in a text message, and not in anyone's memory.

Match the VIN on the contract to the VIN on the car.

Seventeen characters, read one at a time, from the plate at the base of the windshield or the sticker in the driver's door jamb. Not from the brochure, not from the listing — from the vehicle you are about to own. This takes fifteen seconds and catches the rare but genuinely miserable error of paperwork drawn up for a similar car on the same lot.

While you're there, check the odometer figure on the disclosure against the number currently on the dash, and check the year, model and trim. A trim level typed wrong follows the car into its title and its insurance and is tedious to unwind later.

Find the APR box and compare it to the rate you were quoted.

A retail installment contract carries a set of federally required disclosures in their own boxes: the annual percentage rate, the finance charge, the amount financed, and the total of payments. The APR is the one to check first, and the useful question if it has moved is not what's my rate but what rate did the lender approve me at. Dealerships are generally permitted to write a contract above the approved rate and keep some of the difference. That's legal and it's disclosed in the sense that the number is printed in front of you — it is just rarely explained.

Then check the amount financed. It should be the out-the-door total from 20:00, minus your down payment, minus whatever equity your trade carries. If it's larger, something was added between those two numbers.

Count the months. Then read the total of payments.

The term is the easiest thing in the deal to move and the easiest to stop noticing, because it changes the payment without changing the price. If the monthly number came down at some point in the afternoon and nothing else visibly changed, the months almost certainly went up. Seventy-two and eighty-four month contracts on used cars are common now and are not automatically a bad idea, but they should be a decision you made rather than one that arrived.

The total of payments box tells you what the whole thing costs. Compare it to the price of the car. If the gap is uncomfortable, that is real information, and the fix is a shorter term or a larger down payment, not a different feeling about it.

Look for anything on the contract you did not ask for.

Service contracts, gap coverage, VIN etching, paint and fabric protection, key replacement, tire and wheel, nitrogen in the tires. Each of these should appear as its own line, with its own price, and most require their own signature or initial. If any of them is present and you did not request it, it comes off — that is a straightforward request and it does not require a debate.

Some of these are genuinely worth buying — gap coverage in particular can make sense on a long loan with a small down payment. The reliable test is that anything worth buying today is still worth buying on Thursday, so a product that can't survive being thought about overnight is telling you what it is. Ask what it costs as a cash number, not as an effect on the payment.

Confirm the payoff amount, who sends it, and by when.

If you're trading a financed car, the dealership is agreeing to pay off your existing loan. Find the payoff figure on the paperwork and check it against the quote from your own lender, including the good-through date — payoff quotes expire, and interest keeps accruing until the check actually lands. Ask what happens if the payoff comes up short, and get the answer in writing on the contract rather than as reassurance.

Then keep making your payment if one falls due before the loan closes out. A payoff in transit is not a payoff received, and your credit file doesn't know the difference. Any refund of overpaid interest gets sorted out afterward; a missed payment doesn't.

Nothing blank. Anywhere. Then sign.

Turn every page over. Any empty field on a document you are signing — a price, a date, a mileage, a term, a name — gets filled in or crossed out before your pen touches it, including on the forms nobody reads. If something is meant to be corrected later, it gets corrected now, and if it genuinely can't be, the signing waits.

Ask directly whether the financing is final and approved, or whether the sale is conditional on approval that hasn't happened yet. Those are different deals, and the second one can bring you back to the desk for a different rate. Then take a full copy of everything you signed before you leave, and photograph the signature pages with your phone on the way out. It takes a minute and it is the cheapest insurance in the building.