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. It is not an
identity document. Unless an organization can demonstrate that the reason it is requesting an individual's SIN is specifically permitted by law, or that no alternative identifiers would suffice to complete the transaction, it 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, financial institutions that provide interest on deposits, 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 a 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. ==Temporary SINs==