Are you u sing the Desktop program? Apparently you can not efile a prior year amended return from the Desktop program.
On Feb 20, 2024 an employee posted this……..
According to our tech support team, this is not a product defect. TurboTax Desktop for prior years does not support E-file for amendments like TurboTax Online does. Apparently, the signature date is the trigger for rejecting an e-file attempt.
https://ttlc.intuit.com/community/after-you-file/discussion/tt-desktop-won-t-let-me-e-file-2022-amen...
