How can I get license keys for legacy versions of TurboTax Business Incorporated 2016 to 2023?

[TurboTaxSusan]

@Sacheen Unfortunately, we no longer sell codes for TurboTax Desktop from before 2018. 

Also, you can't "redo" your 2016 return if you have already filed it. You would need to make an adjustment using the Canada Revenue Agency’s (CRA) My Account service or you can print & mail a T1-ADJ T1 Adjustment Request.