A bill of sale transfers the ownership of personal property from one person to another. It should not be used for the sale of automobiles, recreational vehicles, boats, or other high-value items. A bill of sale for motorized vehicles has special requirements such as recording the vehicle ID number, mileage, etc.
The sale/purchase is complete once both parties have signed the document, payment has been made, and the property has been transferred to the buyer. If the item you’re selling or buying is of high value, you might want to consider having the form notarized. This is a recommendation and not a legal requirement.