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Medicare ID Validator

Finance & Global IDs

Validate a US Medicare Beneficiary Identifier (MBI) format instantly. Checks the 11-character alphanumeric structure per CMS specifications. Free, client-side.

Reviewed by the thecalcu.com team · Last updated July 13, 2026

🇺🇸This tool is specific to United States

What is a Medicare ID?

A Medicare ID validator checks whether a given Medicare Beneficiary Identifier (MBI) follows the 11-character format defined by the US Centers for Medicare & Medicaid Services (CMS). The MBI is the identification number on every US Medicare card and is used in all healthcare billing, insurance claims, and eligibility verification transactions involving Medicare.

The MBI replaced the previous Health Insurance Claim Number (HICN), which was derived from the beneficiary's Social Security Number, between 2018 and 2019 as part of a CMS initiative to reduce identity theft and protect beneficiary privacy. Unlike the HICN, the MBI is a randomly generated 11-character code with no relationship to any personal identifier.

The MBI follows a precise alphanumeric pattern: specific positions must be digits, others must be letters from a restricted 19-letter alphabet (excluding S, L, O, I, B, and Z to avoid visual ambiguity), and some positions may be either. The validator checks all 11 positions against these CMS rules, flagging any position that does not conform.

This is a format check only. It confirms the structural correctness of the identifier, the same check a CMS billing system performs before accepting a claim. It does not query the CMS beneficiary database and cannot confirm whether the MBI belongs to an active beneficiary. Use it alongside the NPI Validator and the EIN Validator when building healthcare billing validation workflows.

Why Use a Medicare ID Validator?

Healthcare billing systems submit tens of millions of claims to CMS daily. An MBI with a character in the wrong position, a letter where a digit is required, or a forbidden letter like O or I, will be rejected immediately. The rejection triggers a resubmission cycle that delays provider reimbursement by days or weeks.

Validating MBI format at the point of data entry, in patient intake forms, EHR systems, and billing software, catches transcription errors before they reach CMS, eliminating the most common cause of claim rejection.

Who Should Use This Validator?

Healthcare billing specialists who enter MBIs into claims management systems can use the validator to confirm format correctness before submission, reducing rejection rates.

EHR software developers building patient intake and billing modules can use the validation logic as a reference for implementing MBI format checks in their applications.

Medical coding professionals who transcribe MBIs from paper or verbal sources into billing systems benefit from a quick format check to catch the most common errors (forbidden letters, wrong position types).

Healthcare compliance officers auditing patient records for data quality can use the validator to identify records with malformed MBIs that need correction.

What Insights Does the Medicare ID Validator Give You?

A valid result shows the MBI in the standard hyphenated display format (e.g. 1EG4-TE5-MK72) and confirms the format check passed. An invalid result lists the exact positions that failed: which position had a forbidden letter, which had a digit where a letter was required, and so on. This pinpoints the transcription error precisely.

How to use this Medicare ID calculator

  1. Enter or paste the MBI into the Medicare ID (MBI) field. You can include or omit the hyphens.
  2. The result shows immediately: Valid with the formatted ID, or Invalid with a list of which positions failed and why.
  3. Correct any flagged positions and re-validate.
  4. For billing purposes, always confirm the MBI against the beneficiary's physical Medicare card.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The 11-character MBI follows this positional pattern (C = required letter, N = required digit, A = letter or digit):

| Position | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Rule | Digit 1–9 | Letter* | Letter* or digit | Digit | Letter* | Letter* or digit | Digit | Letter* | Letter* | Digit | Digit |

*Allowed letters: A, C, D, E, F, G, H, J, K, M, N, P, Q, R, T, V, W, X, Y (19 letters; excludes S, L, O, I, B, Z).

Valid example: 1EG4TE5MK72Invalid examples:
- 0EG4TE5MK72, position 1 is 0 (must be 1–9)
- 1OG4TE5MK72, position 2 is O (forbidden letter)
- 1EG4TE5MK7, only 10 characters (must be exactly 11)

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Frequently Asked Questions

What is a Medicare ID (MBI)?
A Medicare Beneficiary Identifier (MBI) is the 11-character alphanumeric ID used to identify Medicare beneficiaries in the United States. It replaced the Social Security Number-based Health Insurance Claim Number (HICN) in 2019 as part of a CMS initiative to protect beneficiary privacy. Every Medicare recipient has a unique MBI on their Medicare card.
What format does an MBI follow?
An MBI is exactly 11 characters in a specific C A AN A AN A A NN pattern: position 1 is a digit 1–9; positions 2, 5, 8, and 9 are letters from a restricted alphabet (A–Z excluding S, L, O, I, B, Z); position 3 is either a letter or digit; position 4 is a digit; position 6 is either a letter or digit; position 7 is a digit; and positions 10 and 11 are digits.
What letters are excluded from an MBI?
The letters S, L, O, I, B, and Z are excluded from alphabetic positions in an MBI. S and L are excluded because they resemble digits 5 and 1. O and I are excluded because they resemble 0 and 1. B and Z are excluded as an additional safeguard against misreading. The allowed letters are A, C, D, E, F, G, H, J, K, M, N, P, Q, R, T, V, W, X, and Y.
What is the difference between MBI and HICN?
The HICN (Health Insurance Claim Number) was the previous Medicare ID format and was based on the beneficiary's Social Security Number, making it a privacy risk. The MBI replaced it in April 2018–December 2019. MBIs are randomly generated and contain no derivable personal information, making them safer for use in healthcare transactions.
Does this validator confirm that an MBI is active or assigned to a real person?
No. This tool validates only the format, that the 11 characters follow the CMS-defined pattern. It cannot confirm that the MBI is active, assigned to a living beneficiary, or not fraudulently generated. Confirming MBI authenticity requires access to the CMS beneficiary database.
Where is the MBI shown on a Medicare card?
The MBI appears on the front of the Medicare card, typically labelled 'Medicare Number' or 'Member ID'. It is printed in the format XXXX-XXX-XXXX (with hyphens separating characters 1–4, 5–7, and 8–11). The validator accepts the ID with or without hyphens.
Is my MBI data uploaded anywhere?
No. All validation happens locally in your browser. Your Medicare ID is never transmitted to a server or stored. This is important, the MBI is sensitive health information and should not be shared with untrusted third parties.
Why would a healthcare provider need to validate an MBI format?
Healthcare providers, billing companies, and EHR (Electronic Health Record) systems submit claims to CMS using MBIs. A malformed MBI, one that fails the format check, will be rejected by the CMS system. Validating the format before submission catches transcription errors, preventing claim rejections and reimbursement delays.
Can I use this validator to check a legacy HICN?
No. This validator checks the current MBI format only. HICNs have a different structure (SSN-based, with letter suffixes). If you are working with pre-2019 Medicare identifiers, you will need to verify they have been converted to the new MBI format.
What is the formatted display of an MBI?
The standard display format for an MBI is four characters, hyphen, three characters, hyphen, four characters, for example, 1EG4-TE5-MK72. The hyphens are for readability only and are not part of the 11-character identifier itself.
Who issues the MBI?
The Centers for Medicare & Medicaid Services (CMS) issues MBIs. They are randomly generated and assigned when a beneficiary enrolls in Medicare. The MBI has no derivable relationship to the beneficiary's personal information, it is a random identifier.
Also known as
Medicare ID checkMBI validatorMedicare Beneficiary Identifiervalidate Medicare numberCMS MBI