Form 8594 must also be filed if the purchaser or seller is amending an original or a previously filed supplemental Form. 8594 because of an increase or decrease.Form 8594 is a tax document required in certain business sales where the buyer acquires assets rather than stock or equity. A taxable asset purchase allows the buyer to "step up," or increase, the tax basis of the acquired assets to reflect the purchase price. Who Must File Form 8594? Both the seller and purchaser of a group of assets that make up a trade or business need to file Form 8594.