I work for the federal government and received my W2. In block 14, there is code K and an amount. My instructions on the W2 state that this is pretax dental and vision insurance which is correct. I do have that coverage. However, my tax preparer is confused and says the definition the IRS uses is something totally different. How do I account for this on my 1040. Do I report it or what?

Assume your tax preparer figured it out. The information is superfluous and really has no effect on your return. It can be ignored.