If you have entered the wrong SIN Number and you are already at the REVIEW or FILE section then you will not be able to update it.
You can go to personal information and click on EDIT to update your SIN number. However, If you are unable to do so then you will be required to start a new return. For more information, you can contact CRA How do I contact the CRA?
Thank you for contacting TurboTax.
