Hi,
It would depend on how you filed your previous return.
If you used the Netfile service to file that return in TurboTax, then you can make changes to it by using our ReFILE service. If you didn't use Netfile, then you will have to complete the T1-ADJ form from CRA.
Note: ReFILE service is only available as early as 2017 tax years.
For more instructions on how to change your return: https://turbotax.community.intuit.ca/community/tax-return-amendment/help/i-have-filed-my-tax-return-...
