Beginning March 1, all Medicare claims must contain a National Provider Identifier (NPI). You may submit claims with a legacy number and an NPI or just an NPI, but no longer will Medicare accept claims with just the legacy number.
Physicians who bill Medicare and are being paid for claims submitted with both an NPI and a legacy number are strongly urged to test their ability to get paid using just their NPI. To test this, they should submit one or two claims as soon as possible. This step is critical to ensuring that their claims will be processed without interruption beginning March 1.