How do you write the receipt when you sell your own car?

All that is required in most states is all pertinent information be contained in the bill of sale. Which basically would be, the name of the seller, the name of the buyer, the date the sale was made, the amount the vehicle was sold for. A few states require that a vehicle bill of sale be notarized, whether it is required by law or not it is always a good idea to do so. It is also prudent to include other information that might protect the seller from possible litigation, such as "sold as is" which indicates the seller makes no guarantee as to the condition of the vehicle.