For individuals resident in Canada, their authorized tax identification number is their nine-digit Canadian Social Insurance Number (SIN) issued by Service Canada. Every individual resident in Canada with income tax filing obligations (or in respect of whom an information return is to be made) is required to have (or obtain) a SIN.
SINs are confidential but are required to be furnished on request to financial institutions for tax reporting purposes.
For more information on the SIN, including how to apply for one, go to Service Canada.