If a foreign contractor/vendor (payee) claims that payments are made for income that is effectively connected with a US trade or business, you are required to obtain from him a Form W-8ECI, Certificate of Foreign Person’s Claim That Income Is Effectively Connected With the Conduct of a Trade or Business in the United States, which effectively exempts him from tax withholding as he is to file his own US tax return. In this case, you are not responsible for withholding US tax from your payments to this foreign contractor/vendor. You need Form W-8ECI in order to…