Yes, contributions made to a 403(b) retirement plan are subject to FICA taxes. This means that both employer and employee contributions are liable for Social Security and Medicare taxes.   The 2023 FICA tax rate is 7.65%, with 6.2% allocated to Social Security and 1.45% allocated to Medicare taxes. It's important to note that contributions to a tax-sheltered annuity can be made on either a pre-tax or after-tax basis, depending on the specific rules outlined by the plan.