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.Enter your name and taxpayer identification number (TIN) at the top of the form. Then check the box for Purchaser or Seller. Did you buy or sell a business during the tax year? If so, you may need to file IRS Form 8594 with your federal tax return. For a list of forms and schedules available in ATX, please click on federal forms or select a state. Form 8594 is a tax document required in certain business sales where the buyer acquires assets rather than stock or equity. Note. See instructions before completing this form. Part I. Automatic 5-Month Extension Complete if Filing Form 1065, 1041, or 8804.