conversation: User (ayjayred): "I was wondering what happens if you only worked in November &amp; December for 2014, and contributed 100% of your paycheck to a traditional 401k.  Would the taxes be essentially 0?"
  Self: "&gt;Would the taxes be essentially 0?\n\nYes, actually zero.  401(k) contributions are pre-tax.  If it is all gone (100% deferral) before tax than there is nothing to tax.  "
  swalsh411 (swalsh411): "401k deductions are not pretax for medicare and social security. In most payroll systems if you set up a 100% 401k deduction, it would have the employer pay 100% and kick back some sort of FICA out-of-balance error."
  Self: "Excellent point.  Just wondering why I have seen plan options with an upper deferral limit of 100%.  \n\nI guess you would have to write a check on payday ;o)"
  