Your 401(k) contribution is listed on your W-2 in Box 12 as Code D. Code D represents elective deferrals to a section 401(k) cash or deferred arrangement (or deferrals under a SIMPLE retirement account that is part of a 401(k) arrangement). Do not re-enter your 401(k) contribution anywhere else in TurboTax as it has already been accounted for on your W-2.
