I'm not sure why you can't enter codes for box 12 on your W-2 form entry. You click on the down arrow to the right of the box and choose the code number listed on your form. Code DD is the cost of your employer provided health care. It likely doesn't need to be entered as it is not taxable.
**Say "Thanks" by clicking the thumb icon in a post**Mark the post that answers your question by clicking on "Mark as Best Answer"