Employer Not Withholding Taxes?

So my partner just received their W2. They realized her a long with everyone else had not had their federal withholding taken all year. A little context. The company was bought out by a corporate office at the beginning of the year and gave everyone a small raise, and all payment is direct deposit with pay stubs by request. So nobody noticed until the received their W2. We live paycheck to paycheck and a sudden tax bill of several thousand is basically enough to destroy any chance of financial stability for the rest of the year. Is there any course of action or is the only option to bend over the barrel and take it?