FICA was not withheld from my paycheck
Should I have a W-2 re-issued? A W-2 can be corrected and a new copy will be filed with the IRS if your employer incorrectly reported your income and withholding on a W-2 that they issued. In this case, though the employer didn't withhold those taxes, they should not reissue the W-2 unless they plan to pay your portion of the payroll taxes that were not withheld. (If they paid your share of the taxes, that would increase your gross income.) Who pays for the FICA I should have paid last year? Both you and your employer owe 7.65% each for FICA taxes. By law your employer is required to pay their half and you are required to pay your half. Both you and your employer owe additional taxes because of this mistake. Your other questions assume that your employer will pay your portion of the taxes withheld. You employer could decide to do that, but this also assumes that it was your employer's fault that the mistakes were made. If you transitioned to resident alien but did not inform your employer, how is that your employer's fault?