A boat bill of sale is a contract used to transfer ownership of a vessel from a seller to a buyer. The agreement must be signed by both parties and may also require a witness signature, boat financing lender approval/signature, and in some cases a notary to notarize. The bill of sale should typically only be filled out and signed once the seller has delivered the watercraft to the buyer, and the buyer has remitted payment to the seller. All of these transactions are orchestrated by a professional broker.