Unmarking the IRA/SEP/SIMPLE box implies that the distribution is not from an IRA and would be in disagreement with what the actual Form 1099-R which says that the distribution is from a traditional IRA.
The actual taxable amount of a distribution from a traditional IRA is unknown to the IRA custodian, which is why they are required to indicate the same amount in box 2a as is in ox 1 as the default assumption and to mark box 2b Taxable amount not determined. The actual taxable amount is determined on your tax return, in this case by your own entries into TurboTax.
Other than indicating that you rolled the entire distribution over to another traditional retirement account, which would be indicated on Form 1040 line 4b with the ROLLOVER notation, there are only three reasons that the taxable amount included on line 4b would be zero when the amount is included on line 4a:
- You have indicated that the entire amount was transferred to a Health Savings Account ("HFD" notation present next to line 4b),
- You have indicated that the entire amount was paid directly to charity as a Qualified Charitable Distribution ("QCD" notation present next to line 4b), or
- You have reported basis in nondeductible traditional IRA contributions in excess of the amount distributed and you have indicated that on December 31 you had no balance in traditional IRAs such that the taxable amount calculated on Form 8606 Part I is zero.
It's doubtful that #1 or #2 are the case, otherwise you would probably already know these to be the cause. That leaves #3 which I addressed in my previous reply.
