An Asset Purchase Agreement is an agreement between a buyer and a seller of a business as to the terms and conditions of the sale of the business. A purchaser of the assets of a business will be liable for any unpaid sales tax of the seller, as well as any accrued interest and penalties related thereto.The documents you need to buy or sell a business depend on the structure (discussed here) and complexity of the deal as well as its specific terms. In an asset purchase, the buyer agrees to purchase specific assets and liabilities. This means that they only take on the risks of those specific assets.