也有不報的情況，見鏈接中描述的案例

Jacques Dubois, who is a resident of the United States under Article 4 of the U.S.-France income tax treaty, receives French social security benefits. Under Article 18(1) of the treaty, French social security benefits are not taxable by the United States. Mr. Dubois is not required to file a Form 8833 for his French social security benefits or report the benefits on Form 1040.
http://www.irs.gov/publications/p519/ch09.html#en_US_2014_publink1000222739