We both made roughly the same amount ~22,000 but my wife actually owes money this year. After looking at our w2s it looks like her withholding is significantly lower than mine (about a third of what was withheld from me). Why is this ? We both only have our w2s no extra forms and we both made around the same both are residents of the same state so why was her withholding so low throughout the year that now she owes money ?
That would be the result of the W-4 she filled out with the employer; she did not have enough tax withheld. Going forward, she can complete a new W-4 and have more tax withheld to avoid having to pay tax when you file your return.
I had a similar result last tax year. When the tax laws were changed in 2018, personal exemptions were eliminated. To try and make up the difference the standard deduction was increased. Some employers / employees made changes to their withholding amounts to avoid the surprise you had.
The IRS has a web site to help you calculate the year end result you want as well as showing what values to enter on the new W-4 form.
Have your most recent pay stub available so as to enter some dates and dollar values in the estimator.