Your contributions should be in Box 9. The program will calculate the taxable portion using the Simplified Method.
The Simplified Method
Generally, if you begin receiving annuity payments from a qualified retirement plan, you use the Simplified Method to figure the tax-free part of the payments. A qualified retirement plan is a qualified employee plan, a qualified employee annuity, or a tax-sheltered annuity plan or contract (refer to Publication 575 for definitions). Under the Simplified Method, you figure the taxable and tax-free parts of your annuity payments by completing the Simplified Method Worksheet in the Form 1040 Instructions or in Publication 575. For more information on the Simplified Method, refer to Publication 575, or if you receive United States Civil Service retirement benefits, refer to Publication 721, Tax Guide to U.S. Civil Service Retirement Benefits.