For starters it is a requirement by law that the employer do withholding.
https://www.irs.gov/payments/tax-withholding
There is no stipulation that anyone must look at their check and decide whether it is proper or not so whether my spouse looked at the check amounts or not or knew what those things were or not - is irrelevant.
So that is why I would expect that the IRS would consider that the employer did not fulfill their part, therefore I should not be held accountable for their error.
