​A health maintenance organization (HMO) is an organization that provides managed care for health insurance contracts in the United States as a liaison with health care providers (hospitals, doctors, etc.). The Health Maintenance Organization Act of 1973 required employers with 25 or more employees to offer federally certified HMO options if the employer offers traditional healthcare options. Unlike traditional indemnity insurance, an HMO covers only care rendered by those doctors and other professionals who have agreed to treat patients in accordance with the HMO's guidelines and restrictions in exchange for a steady stream of customers.