Filing

If you are able to ReFile your changes, and you prepared your returns with your spouse, then you can add the transfer and ReFIle both returns at the same time. For those years that you have to mail in (2015 to 2020), you can send still send adjustment requests for both you and your spouse (to claim the credit and do the transfer).

This TurboTax Canada FAQ tells you how adjust a NETFILEd return using ReFile: https://turbotax.community.intuit.ca/turbotax-support/en-ca/help-article/accounting-bookkeeping/file... ReFile is not available for TurboTax Online 2021 or earlier, or TurboTax Desktop 2019 or earlier.

This Canada Revenue Agency (CRA) web page lists other ways to can adjust your return: https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/change...