Hi mere164, thank you for reaching out with your question. 

This code, which is made up of numbers and letters, can be found on your paper Notice of Assessment (NOA) top right corner under the “Notice Details” section ( see image below) or online in your “MyAccount” next to “Access Code”. This code is unique to each individual.

You can refer to our tax tips page for more details - https://turbotax.intuit.ca/tips/netfile-access-code-nac-12156