You would enter it under the option for 401(k) in the Self-Employed Retirement Plan section. The main difference between the 401k and 403(b) is the eligible type of organization and the other differences don't apply to self-employment. For self-employed retirement, if you are a self-employed minister, then you would still be able to deduct your contributions to a 403(b) on Line 28 of Form 1040. In TurboTax, entering this under the heading for 401k will yield you this result.