Old Age Security
The Old Age Security pension (or OAS or OAS-GIS) is a taxable monthly social security payment available to most Canadians 65 years of age or older. As of January, 2012, the basic amount is C$540.12 per month. At tax time, recipients with 2010 incomes over C$67,668 must pay back a portion of their Old Age Security at a rate of 15% of net income. This is often referred to as a clawback. The OAS pension is fully clawed back for people with incomes over C$110,878.
Eligibility Criteria 
A person must apply to Department of Human Resources and Skills Development Canada (HRSDC) and meet the eligibility criteria to receive benefits.
Full Pension 
To receive a full OAS pension, a person must meet these conditions:
Category 1 - Lived in Canada for at least 40 years after turning 18, OR Category 2 - Born on or before July 1, 1952, AND between the time the applicant turned 18 and July 1, 1977, the applicant lived in Canada for some period of time, AND the applicant lived in Canada for the 10 years immediately before the application was approved.
If an applicant has not lived in Canada for all of the last 10 years because he/she gave up residence in Canada at some time, an applicant may still qualify for a full pension if he/she meets both conditions below:
1) Lived in Canada for the year immediately before the application was approved, AND 2) Prior to these last 10 years, the applicant lived in Canada after age 18 at least 3 times as long as the total of absences during the last 10 years.
Partial Pension 
If an individual does not qualify for a full pension, he/she may qualify for a partial pension if he/she meets these conditions:
Social Security Agreements 
Canada has social security agreements with a number of countries. These agreements may allow a person who has lived in Canada and another country (for example, the U.S.), to count years spent in the other country to qualify for the OAS pension. Note that this is to qualify, and that only time actually spent living in Canada will be counted in determining the amount of the pension.
For low income pensioners who earn little or no other income, the Old Age Security is supplemented by a Guaranteed Income Supplement (GIS), which is considered non-taxable income. The amount of the Guaranteed Income Supplement depends on income, marital status and the age of the spouse in married couples. As of January, 2012, the maximum supplement for a single individual with no other source of income is C$732.36 per month, and C$485.61 per month to each spouse of a married couple.
Old Age Security should not be confused with the Canada Pension Plan, which is a contributory, earnings-related pension paid in addition to the OAS to those who have contributed to it.