In terms of being used for authentication, CRA and other online services usually require SIN + DOB + Postal Code, and then they mail you a 4-digit PIN to the ad

In terms of being used for authentication, CRA and other online services usually require SIN + DOB + Postal Code, and then they mail you a 4-digit PIN to the address they have on file. Hilariously enough, if you call them, you can change the address on file if you have SIN + DOB, making the "PIN" pointless (and irritating, since you have to wait several weeks)