I'm not sure how you can cause this distribution to be treated as nontaxable (entirely excluded from Form 1040 line 5b) unless you either indicated that you rolled the distribution over or you used the Simplified Method or the General Rule to indicate that less that the full amount is taxable. I would print out TurboTax's 1099-R for for this entry and examine TurboTax's Additional Distribution Information and the Simplified Method Worksheet to see if these explain why no part if this distribution is appearing on Form 1040 line 5b.
Given that there is no code D in box 7, I assume that this is a distribution from a qualified plan, perhaps a pension plan. If you have no after-tax basis in the plan, the entire amount is taxable. It would only be made nontaxable by applying the Simplified Method and indicating some nonzero plan cost (your after-tax investment in the plan). If you are unable to substantiate any after-tax investment in the plan, the entire amount is taxable.
