1099-R from OPM if box 2 is blank or state unknown you have to put in the same amount that is in box 1 into box 2 in order for the pension or annuity to be taxed properly. Leaving box 2 blank will not tax the full amount that is listed in box 1 which make the taxpayer receive a larger refund.
https://www.opm.gov/retirement-center/
FAQ: If your 1099R Statement Box 2.a for the Taxable Amount is marked as 'Unknown'; this means that OPM did not calculate the tax-free portion of your annuity. Some of the most common reasons for not calculating the tax-free portion of your annuity:
