How do I claim unused Canada Training Credits from previous years?

Any amount of Canada Training Credit that you have not used will be shown on your 2020 Notice of Assessment (NOA). 

To change the Canada Training Credit Limit on your return in TurboTax Online: 

1. Go to Your Student Profile by selecting Find from the menu
2. Enter student in the search bar, then choose Students from the list of results and select Go
3. Check off "Tuition fees on receipt, T2202, or TL11", and then click the “Continue” button until you see the Canada Training Credit screen.
4. Remove any amount in the box and then click the “Continue” button.
5. On the next page, answer No to the question “Do you want to claim the Canada Training Credit?”. Click the “Continue” button to save your changes.

This Canada Revenue Agency (CRA) has more information on the Canada Training Credit: Canada Training Credit