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. Further, the parties should agree to file a supplemental Form 8594 to reflect any such increase or decrease. This form provides the IRS with a detailed breakdown of how the purchase price is allocated across different asset categories. Learn how to file form 8594 and when to file. – The Form 8594 must be attached to each filer's timely filed Federal income tax return. According to section 1060 of the Internal Revenue Code, the IRS requires that you fill out and file Form 8594 when you're buying or selling a business.