On my Form 1099R Box 16 State Distribution is blank but the program wants something in that space.

[prc1234]

Simply enter the taxable amount shown in 2a on your 1099 (assuming your state taxes your income).

[SteamTrain]

Generally, many of us recommend putting the box 2a value in there...as long as box 2a has an actual non-zero value in it.

If box 2a is empty, or marked as being "undetermined"....then as long as you didn't put make an "After-tax" contributions to that type of retirement account, then you could likely just enter the box 1 value into box 16.