Nonresident Withholding. What are the withholding rates for foreign. (non-U.This is recorded and reported each tax year via IRS Form 1042S. What are the withholding rates for foreign. (non-U. Setting aside the work permit issue, a foreign contractor working in the US should pay tax on his US sourced income. In other words, nonresidents pay California income taxes on taxable Californiasource income.