The code DD in box 12 on your W-2 refers to the sum of what you and your employer contributed to your health care coverage. The amount with code DD has already been removed from wages in boxes 1, 3, and 5.
Please enter the codes and the amounts in the corresponding boxes in the W-2 interview in TurboTax.
For a complete list of the codes, please see https://ttlc.intuit.com/replies/3300234
