Medicare Beneficiary Identifier (MBI)
Use Medicare Beneficiary Identifiers (MBIs) for all Medicare transactions. The Centers for Medicare & Medicaid Services (CMS) replaced the Social Security Number (SSN)-based Health Insurance Claim Numbers (HICNs) with the MBI and mailed new Medicare cards to all Medicare beneficiaries. The cards with MBIs offer better identity protection. With a few exceptions, Medicare will reject claims you submit with Health Insurance Claim Numbers (HICNs). Medicare will reject all eligibility transactions you submit with HICNs.