Yes, FICA (Federal Insurance Contributions Act) withholdings are mandatory. FICA withholdings include taxes for Social Security and Medicare, and they are required by federal law. Both employers, who handle employee paychecks, and self-employed individuals are obligated to pay FICA taxes. These taxes are separate from federal income taxes. Social Security and Medicare taxes are components of FICA, but FICA itself encompasses more than just these two taxes.