@karlarson
That is an extremely common problem....thousands of times so far this year, because most payers of 1099-R forms don't put anything in box 16.
________________
To solve this problem:
1) If box 2a of your 1099-R form has a positive non-zero number in it, copy that value into box 16.
OR
2) If box 2a is empty or "Undetermined", you need to enter the Federally-taxable amount of box 1 into box 16
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*