If there's no amount in Box 14 of your Form 1099-R, you can leave box 14, 14 and 16 blank. If Box 14 has an amount, than the amount for Box 16 would be the same as Box 2a Taxable Amount. If box 2a is blank, and you made no after-tax contributions to your account, you can use the amount in Box 1.
Box 16 on Form1099-R is for state distributions. Many states require box 16 to be completed, but not all.
Click here for the IRS instructions for Form 1099-R.
Click here for instructions on where to enter your Form 1099-R.
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