I was about to mail my 1040X for 2016 but I believe that I am under reporting the income. On the 2016 F5329, I'd only entered the 6% tax/penalty on the excess contribution for 2016, which I then put on line 10 on 1040X. I showed no other income difference from my 2016 tax filing. But I believe I need to enter an income amount on line 1 of 2016 F5329. Box 2a on 1099-R entry for 2016 (J) is blank (box 2b is checked). However, the amount in Box 1 is larger than my excess Roth IRA contribution. Do I just put the difference of Box 1 (1099-R) and 2016 excess Roth contribution as the taxable distribution/income on line 1 of F5329? Then add 10% of that (line 4) to the amount I have on line 10 on 1040X?
I did not make any other Roth contributions or get any distributions besides this (I have only one Roth account).
