Turbo Tax does calculate the amount for box 2a on your Statement of Annuity Paid form, from OPM.
When you get to the screen with Taxable Amount, click "No, a different amount ..."
Then, I used the "Simplified Method" which I believe is required, to calc. the Taxable Amount. Box 9b on the 1099-R has your Contributions, which you need to enter.
Note:
(I have not yet been able to get TT to USE this taxable amount!)
