New line 3b has been added to this form. Complete Part XI. Nonreporting IGA FFI.Welcome to the Maricopa County Treasurer's IRS Forms Page. This page provides links to the IRS Tax Forms. Foreign vendors do not complete the Substitute Form W-9; foreign persons or entities must submit one of five available forms. Only USbased companies need to collect Forms W8 or W9. If a company is based outside of the US, there's no need to collect them. Enter your 5 digit zip code. A 4 digit add on is optional. Arizona transaction privilege tax (TPT) is a tax on the vendor for the privilege of doing business in the state.