For some (myself included) it takes a long time to figure out Form 8606 even if you have examined it and studied Pub590 many times.
Eventually you will understand.
Otherwise you have to answer the TurboTax step-by-step questions exactly correctly for correct results.
Sometimes the questions are misleading !
the two main factors determining the taxable amount are:
your basis.
your total IRA value at the end of the tax year
This is an over-simplification, since there are other factors.
