This question is assumed to relate to the income tax treatment of cross-border social security benefits, rather than to the taxation of pensions generally.
Based on figures provided by the United States Government, the total number of residents of Canada receiving U.S. social security benefits is estimated to be about 81,000. It should be noted that this figure may include persons temporarily in Canada and others who would not be considered residents of Canada for income tax purposes. It also includes recipients who are U.S. citizens, and who are thus liable to U.S. tax on all of their income. The number of
recipients is thus significantly greater than the number who are subject to U.S. withholding tax.
No information is available as to the number of native Canadians who receive U.S. social security benefits. The Canada-United States Income Tax Convention does not make any special provision for native Canadians. The convention would probably not preclude the United States from choosing, as a matter of internal policy, to provide more favourable treatment to native Canadians than to other Canadians. The Government of Canada is not aware of the United States having implemented any such policy.