Social Insurance Number (SIN)
A Social Insurance Number (SIN) is the nine-digit federal identifier Canadians use for work and government benefits — one of the most sensitive pieces of personal information an organization can hold.
The SIN is issued by Service Canada and is required to work in Canada and to access government programs. Because it links directly to tax, employment, and benefit records, a leaked SIN is a prime target for identity theft.
There is no general law forcing you to hand over your SIN to a private business. Federally, only specific programs (employment income, tax reporting, certain financial accounts) are legally entitled to collect it. Collecting a SIN as a customer ID or general lookup key is discouraged by the Office of the Privacy Commissioner of Canada.
If you do collect SINs, treat them as high-sensitivity data: limit collection to lawful purposes, restrict access, encrypt at rest and in transit, and never use them as usernames or file names.
