You can still file your tax return even if your employer didn’t collect enough Social Security and/or Medicare taxes from your wages.
It’s recommended that you discuss the error with your employer and work out an agreement. The employer should withhold the correct amount of taxes from your wages, but until the IRS receives the additional tax that needs to be paid, you will be liable to pay the difference.
You and your employer must pay a share of Social Security and Medicare taxes on the wages you earned. Generally, your employer should withhold 6.2 percent and 1.45 percent of your wages for Social Security and Medicare taxes, respectively.
For more information, see IRS Publication 15 and search for “Collecting underwithheld taxes from employees.”