[Excerpt] Most civilian federal employees who were hired before 1984 are covered by the Civil Service Retirement System (CSRS). Under CSRS, employees do not pay Social Security taxes or earn Social Security benefits. Federal employees first hired in 1984 or later are covered by the Federal Employees’ Retirement System (FERS). All federal employees who are enrolled in FERS pay Social Security taxes and earn Social Security benefits. Federal employees enrolled in either CSRS or FERS also may contribute to the Thrift Savings Plan (TSP); however, only employees enrolled in FERS are eligible for employer matching contributions to the TSP.