What Does Box 12 Code B Mean on a W-2?
Uncollected Medicare tax on tips. 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 B is uncollected medicare tax on tips.
What Code B means
It appears for the same reason as Code A, high tips relative to regular wages left too little to withhold the full Medicare tax.
Does Code B affect my taxes?
This is Medicare tax on tips your employer couldn't collect from your pay. Like Code A, you owe it and it's added to your total tax on Schedule 2.
Where to find Code B 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 B. 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.