A taxable asset purchase allows the buyer to "step up," or increase, the tax basis of the acquired assets to reflect the purchase price. 1.2 Agreement to Purchase.Sloppy construction of the asset purchase agreement could cause a mostly tax-exempt transaction to become completely subject to sales tax. An APA is a legallybinding contract between a buyer and seller that finalizes the terms and conditions of an acquisition. An APA spells out the conditions and terms under which a seller will transfer all of the assets that belong to the business to a buyer.