A sales and purchase agreement (SPA) is a legal contract that obligates a buyer to buy and a seller to sell a product or service. An SPA serves as a basis for a transaction to take place, providing a framework of how the transaction will proceed, what is included in the transaction, and, if necessary, what is excluded from the sale. It allows the buyer and seller of a particular asset to negotiate, and ultimately agree upon, a proper price. It is a way of finalizing the interests of both parties before closing the deal. See Purchase Agreement.