If I have any amount shown on my W-2 Box 12 like code C, DD, P, etc does it mean that none of those can be deducted?

yatoshura · ‎June 4, 2019

Does it also mean that all the box12 amounts are nontaxable and not included in box1, 3 and 5 of my W-2?

Is 401K included in Box1? Can it be deducted?