What code and amount should be entered in box 12a - 12D?

[dmertz]

Enter whatever codes and amounts appear in box 12 of the W-2 provided to you by your employer.

[cameaf]

Usually, the information that is needed for those boxes are shown on the W-2 you  are entering. If it is blank on your W-2, you can also leave those boxes blank when entering into TurboTax. Those codes represent certain deductions that were take out of your check such as insurance and 401-k.