Why isn’t Turbo Tax letting me exclude my teacher retirement pension on line 28a? How can I do this manually?

You're on the wrong line . Enter manually and you will be filing incorrectly.'

28a) is not for your General Rule excluded amount. That goes on Line 20b).

20a) is your net taxable pension after the excluded amount is subtracted.

If 100%, 20a) will be zero.

@ssbs14