Question: Our practice has a new physician coming on board to replace a retiring doctor. When can I start billing for his services? Does it matter when he gets credentialed with the insurance companies? Ohio Subscriber Answer: When you can bill for a new physician's services does depend on when you're able to get him credentialed. You'll also need to know the differences between the payers you'll be reporting the services to. Medicare: The date depends on how you're submitting the application as well. If you submit the application via the Provider Enrollment, Chain, and Ownership System (PECOS), you have 30 days from the day you submitted the enrollment application to the Medicare carrier (the date of filing Internet-based PECOS applications is the date the contractor receives an electronic version of the enrollment application and a signed certification statement). If you file a paper application, the filing date is the day the carrier receives your application in the mail, however. Don't start counting from the day you put the application in your mailbox. Private payers: Warning: Alternative: Best bet: