you have made a grave error. if your compensation is $400 and you contributed it to a 401(K) plan there is no compensation left for you to have withholding. you are in effect ending up with a negative paycheck which is not possible. in addition, you have no money left to pay your share of fica and medicare taxes.
you're probably going to need a pro to fix your w-2, 941, and make sure the S-Corp return reflects everything properly. you may also need to have any state Unemployment Compensation returns fixed.
if you made this error, what other errors! this sounds like it's the first year for the S-Corp. you should really use a pro to prepare the first-year return because things that are wrong or out of whack can generate an IRS audit which can end up costing you a lot more than what a pro would charge. then next year you could switch to TT business. No need to tell the pro that.
for example, does or will the S-Corp return show a loss? if so do you have enough tax basis to deduct it on your personal return.
