Deductions & credits

I agree with rebab.  Code W is only for HSAs (including HSA contributions through a Cafeteria plan).  But only for HSAs.

I would bring a copy of the instructions for a W-2 to the employer and see what they say about the instructions for Code W.
<a rel="nofollow" target="_blank" href="https://www.irs.gov/instructions/iw2w3/ch01.html#d0e2461">https://www.irs.gov/instructions/iw2w3/ch0...>
<a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/iw2w3.pdf#page=29">https://www.irs.gov/pub/irs-pdf/iw2w3.pdf#page=29...>