Medicare Beneficiary Identifier (MBI) Format Validator

Medicare Beneficiary Identifier (MBI) format validation: the 11-position CMS grammar and excluded-letter rules.

Open the tool → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.

Example

Medicare Beneficiary Identifier: 1EG4-TE5-MK73

Result: Valid MBI: all 11 positions satisfy the CMS position grammar.

The tool opens with these values already filled in. Replace them with your own.

What you enter

Medicare Beneficiary Identifier (11 characters, hyphens optional)

How this is calculated

CMS Medicare Beneficiary Identifier (MBI) format: 11 characters in a fixed position grammar (numeric, alphabetic, and alphanumeric by position), excluding the easily-confused letters S, L, O, I, B, Z. The new Medicare card specification -- format only, not active entitlement. Read the source ↗

A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.