Hi. I'm starting a new job in a new state in the summer, where I will make 90k annual gross salary, which is paid monthly. Initially my wife will not have a job once I start working, so I will fill out my W4 under the assumption that she doesn't work. She will then look for a job and hopefully will get something in a month or two.

Assuming she gets a new job at the same pay as her last job (40k annual gross salary), do we both need new W4s or is it enough to just do hers, to ensure we don't owe tax at the end of the year? The paycheckcity.com W4 assistant told me we would owe $379.17 extra withholding each month (assuming 12 pay periods remaining and no adjustments or deductions). Does this mean, that $379.17 should be withhheld from both paychecks or just one? Thanks.

Married couples must always remember that the first dollar of the SECOND paycheck is taxed at the rate of the LAST dollar of the FIRST paycheck.

In your case, your wife's salary tax rate STARTS at 15% and goes up from there, so you MUST adjust UPWARD your withholding to cover the extra income tax.