ITG FAQ #14 Answer-What are the reasons for backup withholding? Is there any other type of income tax withholding?
The most common situations for backup withholding for Indian tribal governments may be when a vendor or a patron at a gaming establishment does not give their Taxpayer Identification Numbers (TINs) or gives an incorrect TIN.
Another type of withholding occurs with payments made to nonresident aliens, including gambling winnings and per capita distributions. These payments are subject to 30% withholding at the source, in accordance with IRC Section 1441. Per capita distributions based on gaming operations when distributed to nonresident alien tribal members are subject to withholding at the source unless specifically exempt by treaty.