The buyer must confirm the seller’s tax residency status. A seller is considered a foreign person if they are:
The seller can provide a Certification of Non-Foreign Status — a sworn affidavit, made under penalty of perjury, that they are not a foreign person (it is the seller’s own statement, not the unrelated Form W-9). If the seller fails to provide this certification, the buyer must assume the seller is foreign and withhold the tax.