The Medicare Beneficiary Identifier (MBI) is the unique number assigned to every person enrolled in Medicare, serving as the required identification for all health services and transactions. This code, printed on the red, white, and blue Medicare card, serves as the required identification for all health services and transactions. The MBI is now the standard identifier for all Medicare-related business, having fully replaced the previous identification system.
Defining the Medicare Beneficiary Identifier
The MBI is a randomly generated, government-issued identifier designed specifically for the Medicare program. Its primary function is to replace the former Health Insurance Claim Number (HICN), which was based on the beneficiary’s Social Security Number (SSN). This link created a significant vulnerability to identity theft and fraud.
Congress mandated the change to enhance the security and privacy of beneficiaries’ personal information. The Centers for Medicare & Medicaid Services (CMS) introduced the MBI as a non-SSN-based alternative. Since January 1, 2020, the MBI has been the mandatory identifier for nearly all Medicare transactions.
Structure and Security of the MBI
The MBI is an 11-character alphanumeric code unique to each Medicare beneficiary. The combination of numbers and uppercase letters is entirely random, meaning the code does not contain any personal identifying information. This structure significantly increases security compared to the old HICN.
The 11 characters follow a specific pattern of alternating numbers and letters. To ensure readability and prevent confusion, the letter set excludes characters like S, L, O, I, B, and Z, which could be mistaken for numbers. Every person with Medicare receives their own distinct MBI, even spouses or dependents.
How the MBI Is Used in Healthcare
The MBI acts as the official account number and must be used for all transactions related to the program. Healthcare providers, including physicians, hospitals, and pharmacies, require the MBI to properly bill Medicare for services rendered. Failure to use the correct MBI can result in the rejection of claims and delays in payment processing.
Beneficiaries must present their Medicare card when visiting any provider offering services covered under Medicare Part A (Hospital Insurance) and Part B (Medical Insurance). The MBI is also used for administrative purposes, such as verifying eligibility for Medicare Advantage (Part C) and Prescription Drug Plans (Part D), or when processing appeals or making inquiries regarding coverage.
Finding and Safeguarding Your MBI
The MBI is displayed on the front of the Medicare card, just below the beneficiary’s name. If the card is misplaced, the MBI can be retrieved by logging into the secure account on MyMedicare.gov.
Alternatively, the number can be found by accessing a Social Security Benefit Verification Letter through the online My Social Security account. Beneficiaries can also call the Medicare helpline at 1-800-MEDICARE to request their MBI or order a replacement card.
Because the MBI is personally identifiable information, it should be treated with the same caution as a Social Security Number. Only share the MBI with trusted healthcare providers, insurers, or authorized Medicare representatives, and be wary of unsolicited requests for the number.