How the vehicle sales tax calculator works
The out-the-door discipline
Dealers advertise prices; contracts charge out-the-door totals — price + tax + title + registration + doc fees + add-ons. Negotiating on the ADVERTISED price while the CONTRACT runs 8% higher is how $2,000 appears. Request the out-the-door figure in writing (email) before visiting; dealers who refuse it have told you something.
The trade-in tax mechanic
Most states tax (price − trade-in) — a $6,000 trade at 8.25% saves $495 of tax, which effectively raises your trade value by that much vs selling privately. The exceptions (CA, MI, VA, and a few others) tax the full price regardless. This single mechanic changes the sell-vs-trade calculus more than most buyers realize.
Where the fees vary
Doc fees range $0–$900 by state (some capped by law), registration $30–$250+ by state and vehicle, title ~$15–$50. They are mostly non-negotiable and mostly legitimate — the skill is knowing them, entering them in the calculator, and recognizing when an add-on fee is actually a profit line wearing a fee costume.