If you reported a 2016 non-deductible contribution on your 2016 tax return you will have a 2016 8606 form with that carry-forward basis in line 14.
If you entered your 2017 non-deductible contribution in the IRA contribution section you would have a 2017 8606 form with the 2017 basis on line 1. The total of line 1 & 2 will go on line 3.
If you properly entered the 1099-R and said yes to the question that asks is you made nondeductible contributions and entered the 2016 8606 line 14 carry-forward basis and then entered the total 2017 year end value of all Traditional IRA accounts that existed, the the total basis on the 8606 line 3 will be applied to prorate the total basis between the distribution/conversion and 2017 year ens value. If the year end value was zero then all of the basis would be applied to offset the tax.
**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.**
