All providers and suppliers enrolled with Medicare prior to March 25, 2011, will be required to revalidate their enrollment information.
Between now and March 23, 2013, the Medicare Administrative Contractors (MACs) will send out notices on a regular basis to begin the revalidation process for each provider and supplier. You should not initiate the revalidation process until you receive a notification letter from your MAC but, when you receive that notice, please be sure to act promptly.
Further Details on the Revalidation of Provider Enrollment Information
Implementation of Provider Enrollment Provisions in CMS-6028-FC