Foreign Vendor Questionnaire. Substitute Form W-9.Use Form W9 to provide your correct Taxpayer Identification Number (TIN) to the person who is required to file an information return with the IRS. Vendors and payees who submit IRS Form W-9 will be asked to complete Substitute Fonn W-9. 2. Please mark "X" in appropriate boxes when filling out the fonn. Give Form W8 BEN to the withholding agent or payer if you are a foreign person and you are the beneficial owner of an amount subject to withholding. The company I am dealing with requested for a W-9 form. However, upon research I found out that I am supposed to submit a W8 form instead of a W9. Foreign vendors do not complete the Substitute Form W-9; foreign persons or entities must submit one of five available forms. Form W9 is a commonly used IRS form for providing necessary information to a person or company that will be making payments to another person or company.