You should NOT enter this as an IRA contribution.
Please do not report any
contributions (reported on your W-2, box 12, D) as a separate entry in Turbo
Tax. All you have to do is report W2 data in Turbo Tax exactly as it appears on
the form.
The 403(b) plan
contributions you elect to make come directly out of your salary. Since the
contributions are made with pre-tax dollars, your employer does not include
these amounts in your taxable income for the year. At the end of the year, when
you receive your W-2 form that shows your earnings, you will notice that your
wages subject to federal income (box 1) tax are lower because of your 403(b)
plan contributions (box 12). Since the contributions are not counted in your
taxable income to begin with, you do not take a deduction when you file your
return.