A Social Insurance Number (SIN) is a nine-digit number that appears on your SIN card. You need this number to work in Canada or to access government programs and benefits. You can apply for a SIN when you arrive in Canada. There is no fee for a new card, but there is a fee to replace a lost card.
Parents and legal guardians can apply for a SIN for their children. Children 12 years of age or older may apply for their own SIN. The British Columbia Vital Statistics Agency has a program where parents of a new baby can apply for several services with one application, including a birth certificate and a SIN.
You will be asked for your SIN when you get a job. Your employer will use this number to deduct taxes and employment insurance premiums from your pay and send it to the federal government for you. There are also some federal financial programs, like retirement and education savings plans, that require you to have a Social Insurance Number.
You should NOT share your Social Insurance Number because it cannot legally be used by anyone else. See this website for more details: Information about Social Insurance Numbers from Service Canada
To apply for a Social Insurance Number (SIN) take your ID including your passport to a Service Canada location.