Over the next three years, CMS will replace their traditional Health Insurance Claim Number (HICN) patient identifiers with a new Medicare Beneficiary Identifier (MBI). New Medicare Cards will be sent to all Medicare beneficiaries starting in April 2018, and all providers will be expected to have modified their software to accept MBIs by then. Between April 2018 and December 2019, either the HICN or the MBI will be accepted by CMS. After December 2019, the HICN will no longer be accepted.
The MBI will have eleven characters, numbers and upper-case letters only. A 2015 law (MACRA) requires CMS to remove Social Security Numbers (SSN) from Medicare identifiers. You may encounter the new acronym SSNRI, for the CMS SSN Removal Initiative. For more information see https://www.cms.gov/Medicare/SSNRI/Index.html and https://www.cms.gov/Medicare/SSNRI/Providers/Providers.html .