What is COVERED EMPLOYMENT?
COVERED EMPLOYMENT meaning All employment and self-employment creditable for Social Security purposes. Almost every kind of employment and self-employment is covered under the program. In a few employment situations-for example, religious orders under a vow of poverty, foreign affiliates of American employers, or the employer must elect State and local governments-coverage. However, effective July 1991, coverage is mandatory for State and local employees who are not participating in a public employee retirement system. All new State and local employees have been covered since April 1986. In a few situations-for instance, ministers or self-employed members of certain religious groups-workers can opt out of coverage. Covered employment for HI includes all federal employees (whereas covered employment for OASDI includes some, but not all, federal employees).
reference: Centers for Medicare & Medicaid Services