It is not unusual for Box 2b to be blank on Form 1099-R. Unless your 403-B plan allows after tax contributions and/or a Roth 403(b) option, 100% of your distribution will be taxable. If you have distributions from an after tax account or a Roth 403(b) account, they would be reported on a separate Form 1099-R. The tax treatment of the distribution will be determined by the code in Box 7 which you enter into the program.