I'm currently maxing my 401(k) contributions ($18k) and funding my and my wife's Roth accounts ($5500 each). She's currently only contributing $200USD/mo to her 403(b).

Due to us owing an extra $2500 last year, we both changed our W4's to zero exemptions. I also changed my 401(k) contributions from 50% Roth/50% traditional to 100% traditional - in the hopes to help avoid another tax liability this year.

By her changing the W4 exemption from 1 to 0, her net check was approximately $100/month less than before.

So, this question is a springboard off of this question. If she changes her W4 back to one exemption, and increases her 403(b) contribution by $100, will/should the net paycheck be the same? A back-of-the-envelope-round-number answer should suffice. I'm guessing there are other numbers that come into play for a specific answer. She's a teacher in Texas, and does not contribute to Social Security, and I work in the private sector.

Please let me know if there's any other information I need to supply to help arrive at a reasonable answer.


2 Answers 2


Assuming all other things are the same the net pay should work out to be close. In reality if the 403 (b) is pre-tax then then net should be slightly more due to slightly lower withholding, however, the difference should be negligible for the purposes of this calculation.


I believe you are trying to mix issues that are really separate.

Say your wife's W4 shows the correct allowances. Correct meaning that for her it leads to the ideal amount of tax withheld. Now, she bumps her 403(b) deduction. There's no need to go back to the W4 and do anything.

A couple is making $100K and tells me their tax return showed they got no refund, nor owed any money. Absent any quarterly payments, this tells me they nailed their W4 to show the correct withholding. Now, they decide to save $20K pre tax in their 401(k) accounts. That's great, but it doesn't require revisiting the W4 form. The $20K going to the 401(k) comes off the top, so payroll is not counting it when calculating withholding. But, in this scenario, if the told me they plan to deposit $8000 to their pre-tax IRA for this year, that would require a W4 adjustment, unless they are happy to get $1200 back on their tax return.

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