The following IRS link provides "the W-2 instructions that explain what should go in each box of the W-2."
http://www.irs.gov/pub/irs-pdf/iw2w3_11.pdf W-2 Special Items:
1) The cost of employer sponsored health coverage is optional to report for 2011. The reporting would be in
W-2 Box 12 with new Code DD. The cost of the coverage is not taxable and is for informational purposes only. For additional discussion, please refer to IRS Notice 2011-28.
2) Participants in 457(b) plans can now treat elective deferrals as Roth contributions.
This is shown in W-2 Box 12 with new Code EE.
3) The 2011 Form W-3 has changed from 2010. There is a new section for the
kind of employer with 5 designation boxes. Taxpayers are requested to check at least one of these.