Functionality
Through functionality creep, the SIN has become a national identification number, in much the same way that the Social Security Number has in the United States. However, unlike in the US, in Canada there are specific legislated purposes for which a SIN can be requested. Unless an organization can demonstrate that the reason they are requesting a person's SIN is specifically permitted by law, or that no alternative identifiers would suffice to complete the transaction, they cannot deny or refuse a product or service on the grounds of a refusal to provide a SIN. Examples of organizations that legitimately require a SIN include employers, banks and investment companies, and federal government agencies. Giving a SIN when applying for consumer credit, such as buying a car or electronics, or allowing it to be used as a general purpose identification number, such as by your cable company, is strongly discouraged.
The Canadian military used the SIN as a form of unique identifier from the 1960s until the 1980s, when service numbers were reintroduced. Military identification, including ID cards and identity discs were marked with the SIN during this period.
Read more about this topic: Social Insurance Number