Unless you have information from the last Form 8606 that the decedent filed, if any, showing basis in nondeductible traditional IRA contributions, the entire amount is taxable. If you do have such information along with information amount any other traditional IRAs that the decedent had, you must calculate the taxable amount outside of TurboTax using the method on Form 8606 and enter the resulting taxable amount . TurboTax will place this amount in box 2a of TurboTax's 1099-R form.
As for TurboTax's RMD questions, because the distribution to you was not eligible for rollover, you can indicate that the required amount was the amount distributed (or any lesser amount) and that it was all RMD. This will avoid TurboTax preparing Form 5329 Part IX.
