Definitions for "Social Insurance Number"
a unique nine-digit number assigned to Canadian citizens and residents by the federal government for identification purposes.
A number given to each contributor to the Canada Pension Plan, Quebec Pension Plan, and Employment Insurance Plan. It helps record the contributions and premiums paid into and the benefits paid out of the plans. Since these social insurance programs are connected to the tax system, the SIN is also used as an identifier for federal income tax purposes. Everyone who files an income tax and benefit return must provide a SIN.
The Government of Canada assigns Social Insurance Numbers to all individuals with an income or those who pay taxes. Individuals must apply for this number. By law, you are required to provide this number to financial institutions with which you have an interest-bearing deposit account.