Retirement tax questions
The entry you mention would normally be reported by virtue of an amount listed in box 11 on your W-2 form. If you don't have an entry there, TurboTax allows you to make it by checking the box you mention and entering the amount manually.
The question applies to distributions from or taxable social security/Medicare income recognized in the current year by virtue of deferral income from prior years associated with nonqualified deferred compensation or nongovernmental 457(b) plans. As it applies to what you describe, since you don't mention receiving a distribution it is not likely it applies to you. This is the description to Box 11 as listed on the W-2 form:
