The W-2 you got from your employer will have four lines for box 12—labeled 12a, 12b, 12c, and 12d.
Any amount on a box 12 line will also have an uppercase (capital) letter code associated with it. (If there aren’t any capital letter codes in box 12, skip it and move on to box 13.)
In each box 12 line, select the capital letter code from the dropdown and enter the corresponding amount. See the example further down to see what it would look like in the TurboTax CD/Download software.
Important: Don't confuse the lowercase box 12 letter (for example, the a in box 12a) with the capital letters in the dropdown. So, if your box 12a has the letter code D in it, select D (not A) from the dropdown. And if 12a is blank, leave it blank—don't select A.
To enter multiple box 12 amounts, select +Add another box 12 item.