What are hidden fees when buying a car?

"Hidden" fees are usually charges that weren't mentioned until the paperwork: inflated doc fees, prep or reconditioning fees, dealer-installed add-ons, market adjustments, extra transport fees, or optional products like service contracts and GAP rolled into the price. The fix is to request a written, itemized out-the-door quote early and compare it with the final contract. On OffLot, each vehicle page shows an out-the-door estimate and the Build your deal flow ends with a final review page so you can see every line before deciding.