What Does Box 12 Code D Mean on a W-2?
401(k) contribution (traditional, pre-tax). What it means, whether it is taxable, and what to do with it.
By the Easy Guides Editorial Team · Updated for 2026
Box 12 Code D is 401(k) contribution (traditional, pre-tax).
What Code D means
The amount counts toward the annual 401(k) contribution limit. If you changed jobs, add up Code D from every W-2 to check you didn't over-contribute.
Does Code D affect my taxes?
This is what you put into a traditional 401(k) through payroll. It's already left out of your Box 1 taxable wages, that's the tax break, so you don't deduct it again.
Where to find Code D on your W-2
Look at box 12, in the middle-right of the form. It has up to four lines, labelled 12a, 12b, 12c and 12d. Those letters are only line labels. The code you want is the small letter or pair of letters printed next to the amount, and it will read D. If you have more than four entries, your employer issues a second W-2 to carry the rest.
Not the code you were looking for? The full box 12 code list covers every letter, and the W-2 box decoder explains every box on the form.