123amf2978, are you saying that the Form 1099-R does not show the taxable amount in box 2a? If the taxable amount is present and correct, simply indicate either that the box 2a amount is correct or the box 2a amount was used in previous years.
The IRS requires the General Rule to be used for annuities starting before July 2, 1986 and the Three-Year Rule was not used. If the Three-Year Rule was used, the payments are now generally fully taxable. The General Rule in TurboTax requires you to calculate the taxable amount yourself, then simply enter the result, so select the General Rule. TurboTax does not do the calculation for you.
See IRS Pub 575: https://www.irs.gov/pub/irs-pdf/p575.pdf
