Note that the withholding tax for non-residents is a flat rate of 15%, which can be reduced under the U.S. double taxation treaty with New Zealand. The withholding tax rate for non-residents remains at 15% and could be reduced due to the double taxation agreement between these countries. There is no aggregation agreement, it could be an area where Americans living in New Zealand could be subject to double taxation. U.S. expats can get more information about the New Zealand system from the U.S. Social Security Administration….