Box 12 is a general catch-all for recording various types of income. Box 12 consists of four sections, 12a-12d. These are just references to organize the space and don't have any significant meaning.W2 Box 12 uses codes A through HH to identify a general potpourri of miscellaneous forms of income that must be reported to the IRS. Some of these figures are taxable amounts that are also included in wages elsewhere on the W-2, while some represent non-taxable amounts for informational purposes only.