TurboTax 2021 has been decommissioned. You can have access to the saved copies of your returns. TurboTax Online is available from tax year 2022 to 2024 only. You can make changes to a filed tax return by filing an adjustment. The CRA requires that you wait until you’ve received your Notice of Assessment (NOA) before filing an adjustment. In many cases, the CRA will catch the mismatch and automatically adjust your return for you.
For step-by-step instructions, please follow this TurboTax article: I've filed my tax return. Can I still make changes?
