The CRA accepts ReFILE adjustments for 2021, 2020, 2019 and 2018 returns. However, if you used TurboTax Online to file for those years, then we only have 2020, 2021 & 2022 still available.
For those years that you are not able to ReFILE, you can use the Canada Revenue Agency (CRA)’s My Account service to make the changes, or fill out and mail in a T1-ADJ T1 Adjustment Request.