Doing taxes. Getting hit with the "married, two similar incomes and even 0 withholding is not enough" penalty. Or California raised taxes to hell in 2016 considering there's a $2k swing with no real changes from 2015.
Yeah California's tax table above 100k total household income becomes useless. You will end up owing money, even with 0 withholding.
Same thing happened to my wife and I. We ended up having to have extra with held from each paycheck. There was some form we had to file the first time it happened, to remove some stupid penalty they were trying to say we owe.