Is a bill of sale the same as a title?
What a title does
A Certificate of Title is issued by the state DMV (or equivalent). It names the legal owner of the vehicle and is the only document that proves ownership. When a car is sold, the seller signs the back of the title over to the buyer, and the buyer takes it to the DMV to have a new title issued in their name.
What a bill of sale does
A bill of sale records the terms of the sale itself: the parties, the item, the price, the date, and the as-is condition. It's the receipt. Most DMVs require a bill of sale in addition to a signed title when the buyer registers the vehicle — it establishes the purchase price for sales tax and provides a paper trail of the transaction.
You usually need both
In most states, transferring a titled vehicle to a new owner requires: the seller-signed title, a bill of sale, and the buyer completing a title application at the DMV. Missing the title makes registration significantly harder — see "Can you get a title with a bill of sale?" for how that works in the states that allow it.
Items that don't have titles
Not everything has a state-issued title. Trailers under a certain weight, older boats, ATVs, and general property (furniture, tools, livestock) usually only have a bill of sale. In those cases, the bill of sale is the primary ownership record.
General information only — not legal advice. Rules vary by state; verify with your state's DMV or a qualified attorney for your situation.