From Ober Kaler (www.ober.com):
As you know, beginning March 1 of this year, claims without a National Provider Identifier (NPI) number in the primary provider field and claims with only a Medicare legacy number in the primary provider field are being rejected and not reimbursed. Effective May 23, 2008, only the NPI will be accepted for all HIPAA electronic transactions, paper claims (UB-04 and CMS-1500), and Standard Paper Remittance (SPR) advices. This means that, in less than two months, you should no longer report Medicare billing numbers in primary or secondary provider fields if you want the claims accepted, processed, and paid.
Ober|Kaler’s Comments: Interestingly, the NPI may also create new opportunities. Because a legal entity with two or more provider or supplier locations may choose to obtain and use either one NPI for all of its locations or a separate, different NPI for each location, the NPI may address, if not resolve, various dilemmas that are common today (e.g., issues related to contractor jurisdiction, centralized billing, etc.)