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. Enter your name and taxpayer identification number (TIN) at the top of the form. Then check the box for Purchaser or Seller. Directions. San Diego, 15015 Avenue of Science, Suite 200. San Diego, CA 92128-3434, 1-858-385-4700. Unravel the complexities of Form 5471 instructions with our comprehensive guide. Attn: Elias Vamvakas.