To qualify for treaty exemption, you must be a citizen or a permanent resident (generally, a noncitizen who files a resident income tax return) of the "treaty country," and the type of payment must be exempt under that specific treaty. In addition, the IRS requires a U.S. federal identification number, evidence of nonresident alien status (i.e., the substantial presence test), evidence of proper work authorization (i.e., visa), and a properly completed IRS "treaty exemption form" (i.e., Form 8233 for wages, fees, honoraria). Information on tax treaties is available from the IRS (Pub.901, U.S. Tax Treaties).
Note: Although Cornell only grants treaty exemption to nonresident aliens, some treaties have "tie breaker rules." If a foreign national feels he or she qualifies for treaty exemption in spite of the fact that Cornell withheld taxes, the individual can file IRS Form 8833 with his or her tax return and certify to the facts that merit the "treaty-based return position." Cornell cannot act as an individual's tax adviser.