Chapter 1: General Registration Information. You do need bill of sale.You may want to write up an extra thing that both of you sign to CYA but that's not for the DMV. While a bill of sale is generally valid without notarization, there are situations where it becomes a wise precaution. Does a vehicle bill of sale have to be notarized in California? No. When you privately sell a car in California, the Bill of Sale does not need to be notarized. You simply write them a bill of sale. Most states do not require a notary to witness the signing of a bill of sale. The signer must always appear before the Notary during the notarization in California. For most private vehicle sales between individuals, a bill of sale does not need to be notarized to be considered legally valid and binding.