Do you have another W-2 from the same employer, with your income on it? If so, the W-2 with only the box 12 entry is not a separate W-2. It's a continuation of the W-2 that shows your income. Don't enter it separately. Add the box 12 entry with code W as an additional entry in box 12 on the W-2 that has your income. You combine the two W-2s and enter them as if they were one W-2.
