Any sale of an entire business to a single buyer is an isolated or occasional sale, and no tax applies to the sale of any assets made part of such a sale. Asset purchase agreements are a useful way to: Carve out certain assets of a business without taking on liabilities or debt obligations.So when tangible personal property is part of an asset sale, the parties have to determine whether an exemption covers the asset sale. A Stock Purchase Agreement (SPA) is a formal contract that enables businesses to document the buying and selling of company stock between a seller and a buyer.