What Does Box 12 Code S Mean on a W-2?
SIMPLE plan salary reduction contributions. 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 S is simple plan salary reduction contributions.
What Code S means
What you chose to contribute to a section 408(p) SIMPLE retirement plan out of your pay.
Does Code S affect my taxes?
Already excluded from box 1, so you get the tax benefit through a smaller taxable wage figure rather than a separate deduction. It still counts for Social Security and Medicare, which is why boxes 3 and 5 look higher.
What to do about it
Nothing at filing time. It is the SIMPLE plan equivalent of Code D for a 401(k).
Where to find Code S 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 S. 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.