2019 TurboTax's question asking for your 2019 year end balance in traditional IRAs has nothing to do with calculating RMDs. 2018 TurboTax does not calculate RMDs, so it has no reason to ask for your 2018 year year-end balance; it has no need to do so. Entering the year-end balance allows TurboTax to do a correct calculation of the nontaxable and taxable amounts of the traditional IRA distribution that was reported on the Form 1099-R. Without the entry of the year-end value, the calculation result is erroneous because TurboTax assumes a zero year-end balance in the absence of the entry. The correct calculation reduces the erroneously high refund amount or the erroneously low balance due with your tax return.
You can see the calculations on Form 8606 Part I.
