Tax Effect of 100% 401K Contribution

[dhbike01]

My employer allows a 100% pre-tax 401K contribution.  This applies to regluar pay and/or bonus pay.  However, if you always have to pay Social Security and Medicare tax which I believe is 7.65%, what does your check look like if you contribute 100%?  Does anyone have any experience with doing this?  I'm considering contributing 100% of a bonus but don't want to dip into my regular pay to make up for the payroll taxes.

[dandarc]

Talk to HR, but it seems it should be treated similarly to if you were to go over the $17,500 cap - reduce your contribution by SS / Medicare / any health insurance premiums and such that may be due.

[Gone Fishing]

Just call HR and ask how it will work.

I had my wife set her's at 80% one time on a ROTH 401(k) (can't remember what the max was).  HR called her and said there was not enough for taxes so we revised downward.  In retrospect I should have had her contribute to a regular 401(k) instead which would have allowed her to use more of her income.

[LadyStache]

I contributed 100% of a bonus. They took out a small amount of the bonus and applied it to the taxes and the remainder of the bonus went into my 401k.

[wtjbatman]

I contributed 100% of a bonus. They took out a small amount of the bonus and applied it to the taxes and the remainder of the bonus went into my 401k.

Ditto. Signed a form saying I wanted 100% of a bonus put into my 401k, they took out FICA, and contributed the rest.

[Rural]

Talk to HR. I had to work mine out carefully with dollar amounts and a payroll estimator (contributing 100% of my salary to 403b, 457k and HSA. We actually left me getting a check for $75 a month rather than risk going over.