When a physical therapist, occupational therapist or speech-language pathologist in private practice enrolls in the Medicare program, how does the Centers for Medicare and Medicaid Services (CMS) determine the effective date of enrollment and what are the requirements for retrospective billing and how many days can you bill for services prior to the effective date of your enrollment? In this article, I will answer these questions. Question How is the effective date determined? Answer QuestionWhat are the retrospective billing requirements and limitations? Answer QuestionCan you give an example of the difference between Effective Date of Enrollment and Retrospective Billing Date?