In the private practice setting, a therapist must enroll in the Medicare program in order to provide and be reimbursed for outpatient therapy services that are covered by the Medicare program. The application can be completed on paper or online using the Medicare Provider Enrollment, Chain, and Ownership System (PECOS). Once the therapists application has been approved by their Medicare Administrative Contractor, there are 3 dates they need to know. They are the: But what do all these dates mean and when can the therapist begin treating Medicare beneficiaries? In this article, I will answer the following questions: