The amount of the 2017 RMD *itself* was calculated on the 2016 year end value - or should have been. Just as the amount or the missed 2016 RMD must be calculated on the 2015 year end value. That is only for calculating the amount of the RMD. You can do that yourself or the financial institution would do if for you - they also put that amount on the 5498 form that you receive in May.
TurboTax does not calculate the RMD amount so that information is irreverent to TurboTax in calculation the *taxable* amount of the *2017* distributions. That *only* depends on the amount of distributions taken *in* 2017 as reported in box 1 on the 2017 1099-R and the *2017* December 31, total IRA value.
The box 1 amount your 2017 1099-R should be the total of the 2016 RMD amount (calculated on the 2015 year end value) and the 2017 RMD amount (calculated on the 2016 year end value). If the RMD amounts were not calculated correctly then that is water under the bridge for 2017 taxes since those distributions are what they are and the box 1 amount is the taxable amount offset by any pro-rated carry forward basis.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
