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. Learn how to file form 8594 and when to file. 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. 7 Tax year and tax return form number with which the original Form 8594 and any supplemental statements were filed. Tax year and lax return form number wilh which the original Form 8594 and any supplemental stalements were filed.