The Centers for Medicare & Medicaid Services (CMS) is urging every physician who files claims electronically to obtain a National Provider Identifier (NPI) well ahead of the deadline of May 23, 2007. CMS is warning physicians that don't sign up for a NPI in advance of the deadline may see delayed or rejected claims. The NPI is a 10-digit number that does not expire or change used to speed claims processing. For more information, please visit https://nppes.cms.hhs.gov/NPPES/Welcome.do.