Guides
The calculators on this site answer "how much?". These guides answer the question that comes first: do you qualify at all, and do you have to apply? Each one sticks to what Service Canada and the CRA publish and hands off to the calculator for the arithmetic.
Retirement benefits
Old Age Security and the Canada Pension Plan are easy to confuse and work in opposite ways. OAS depends on years lived in Canada and usually starts without an application; CPP depends on contributions and doesn't start until you apply. GIS sits on top of OAS for people with low incomes, with conditions of its own.
Who qualifies for OAS?
Age, legal status and years in Canada, and why most people are enrolled automatically.
GIS eligibility
Where the supplement follows OAS and where it doesn't: travel, sponsorship, income.
Who qualifies for CPP?
The retirement pension, disability benefits and the survivor's pension.