Over the past year, Canadians accounted for one quarter of foreign home buyers, and buyers from China, Mexico, Great Britain, and India accounted for another quarter, according to the National Association of Realtors. Under FIRPTA, a buyer must withhold 10% of purchase price if the seller is a foreign person. No withholding is required if the seller is a U.S. citizen; green cardholder (lawful resident); or resident alien (meets either the physical presence testâ€”present in the U.S. for at least 183 days in the current calendar year; or the substantial presence testâ€”present in the U.S. for a weighted average of 183 days over three years). Foreign buyers must acquire a U.S. taxpayer identification number (TIN). Waiting until the time of sale to obtain a TIN may cause difficulty recovering money withheld pursuant to FIRPTA.