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. The buyer must also file Form 8594 for the transaction. Today's goal is to help you understand the importance of IRS Tax Form 8594 in preparing for sale of your business to a third party… If you're buying or selling a business, the Internal Revenue Service requires you to complete Form 8594. Use this helpful guide to assist you along the way.