W2 - box 1 vs 16 with a Roth 401K

[gmott18]

I am trying to figure out why box 1 is less than my box 16.  After research, i found that this may be due to having a 401K because PA taxes contributions to a 401K.  Well, I dont have a 401K. i have a Roth 401K so that would be taxed at Federal level and at state level.  Now the employer match always goes to Traditional 401K and that wouldnt be taxed at Fed or PA level for those contribs.  So box 16 should equal box 1.  Not sure why it is different.  Maybe it is the pre-tax transportation benefit ?  maybe my employer offers that. I never enrolled in that so i guess that isnt it. Must be a reason.

[rjs]

Ask the payroll department to explain the difference between box 1 and box 16.

[gmott18]

It is just one person and they don't really provided detailed information. I guess I can try. Thx.