Social security tax (FICA) has a limit! 401K NOT immune from FI

For 2009, FICA limit is $6,324, that corresponding to $102,000 in W2 income (6.2%). Anything over that is not subject to FICA. Medicare (1.45%) has no such limit. Obviously, your income is over $102,000, therefore the diff.

401K IS subject to FICA tax,it's only pre-tax for income tax purpose.