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 and seller must both file IRS Form 8594, agreeing to allocate the purchase price based on an agreed fair market value. The purpose of Form 8594 is to determine the treatment of the assets for tax purposes, establish the basis of the acquired assets for the purchaser. Learn how to file form 8594 and when to file.