Overview
To work in Canada or access government programs and benefits, you need a 9-digit number known as a Social Insurance Number (SIN).

Your SIN is private and it is illegal for anyone else to use it. You are responsible for protecting your SIN.

Service Canada is responsible for issuing SINs, which comes in a paper format (Confirmation of SIN letter). If you have a plastic SIN card that has not expired, it is still valid.

For Complete Information: (Link)

If you have lost your SIN info or would like to request your SIN info: (Link)