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.Generally, attach Form 8594 to your income tax return for the year in which the sale date occurred. Learn how to file form 8594 and when to file. Form 8594 is a tax document required in certain business sales where the buyer acquires assets rather than stock or equity. IRS Form 8594 defines seven asset classes to which the entire purchase price must be allocated. How to File for Purchase Price Allocation.