I am going to retire next year. My question is that I have lived 30 years in Canada, and before that, I lived almost 20 years in the UK. Does the time I lived in the UK count towards the OAS calculation? Does the UK have social security agreements with Canada? Thanks.

c&p'd from the Government of Canada

No, time spent living in the UK does not generally count towards the Old Age Security (OAS) pension calculation in Canada. OAS is based on the amount of time a person has lived in Canada after the age of 18, and time spent in other countries is not typically factored in. However, there is a social security agreement with the UK that can sometimes allow for this time to be considered, but only under specific circumstances.

Elaboration:

• OAS Calculation:
  The OAS pension is calculated based on the number of years a person has lived in Canada after turning 18. Specifically, you receive 1/40th of a full pension for each year of residence in Canada after age 18.
• Social Security Agreements:
  Canada has social security agreements with other countries, including the UK, which allow for the time lived and contributed in that other country to be counted towards the OAS calculation in Canada.
• UK Specifics:
  The Canada-UK agreement, specifically Article 8, states that if a person is insured under the Canada Pension Plan (CPP) or a provincial pension plan during their residence in the UK, that time can be considered as residence in Canada for OAS purposes, according to a decision from the Social Security Tribunal of Canada.
• Conditions:
  This agreement is not about qualifying for OAS, but about ensuring that individuals from Canada who work temporarily in the UK are covered under CPP, and those from the UK working in Canada are covered under their own country's pension program, says the Social Security Tribunal of Canada.
• General Rule:
  Generally, if you lived in the UK for a period of time but were not covered by CPP or a provincial pension plan, that time will not count towards your OAS calculation.