Fortunately, non-residents of Canada typically remain eligible for CPP and OAS payments. (It should be noted, though, that in order to receive OAS payments, Canadians living in the US must have lived in Canada for at least 20 years after turning 18.)
The agreement with Canada helps many people who, without the agreement, would not be eligible for monthly retirement, disability or survivors benefits under the Social Security system of one or both countries.
If you are a resident of the United States, these retirement benefits are treated as US social security payments for tax purposes. The benefits are taxed only in the US—not Canada. Essentially, the IRS ignores the fact that these are Canadian retirement benefits and treats them like regular US social security benefits.
You will still receive your PS pension payments regardless of where you take up residence or travel to. You will also receive your CPP even if you live in or travel to another country.
If you have social security credits in both the United States and Canada, you may be eligible for benefits from one or both countries. If you meet all the basic requirements under one country's system, you will get a regular benefit from that country.
If you receive Canadian retirement or pension benefits while living in the US, you should report them on form 1040 or a 1040A (depending on which one you're filing).
If you qualify for Social Security benefits from the United States and a CPP/QPP pension from Canada, and you did not need the agreement to qualify for the U.S. benefit, the amount of your U.S. benefit may be reduced.
You can qualify to receive Old Age Security pension payments while living outside of Canada if one if these reasons applies to you: you lived in Canada for at least 20 years after turning 18. you lived and worked in a country that has a social security agreement with Canada.