Medicare application & billing for a new NP

A physician hires a new nurse practitioner.  The practice sends the provider application to Medicare to obtain a Medicare provider number for the NP. Because the NP was not physically on premise at that time, the physician office had to have her sign application and fax to office, and then the office forwarded it to Medicare – Medicare subsequently sent the application back for an "original" signature — which was secured and sent back. 

Question: NP is seeing patients now — will office be able to retroactively bill for Medicare services performed before the new Medicare number is received?? 

Answer: NP will only be able to bill for services 30 days from date of application being accepted by Medicare for processing (effective date).  Every time you have to resubmit information requested, the date can and will change on the effective date.  Any patients seen prior to the effective date are invalid billings and will not be reimbursed.