If you have a 401(k) or TSP through your employer, your contribution is reported in Box 12 of your W-2 with the letter code D.
Because your contribution is included in your W-2, do not re-enter it in the retirement section.
Individual 401(k) plans for the self-employed (also called solo 401(k) or solo-K plans) are entered in the Other Business Situations section of Income & Expenses in TurboTax.
