What Is Your Medicare Claim Number and What Does It Mean?

Your Medicare claim number contains 11 numbers and letters and is used to identify the services and goods that Medicare is billed on your behalf. You can find your Medicare claim number on your red, white and blue Medicare card.

Your Medicare claim number is the same as your Medicare card number. That means your Medicare claim number is the same as the 11-character series of numbers and letters on the front of your red, white and blue Medicare card.

Medicare uses this number to file and process your claims, using the number to identify you as the beneficiary. Your claim number is also known as a Medicare Beneficiary Identifier (MBI). 

Your Medicare claim number does not use the letters S, L, O, I, B or Z, to avoid confusion. 

Find a $0 premium Medicare Advantage plan today.

Speak with a licensed insurance agent


If you have a Medicare Advantage or Medicare Part D prescription drug plan, you will likely have a card for that plan that also contains a beneficiary identification number. 

Why Medicare uses a claim number

Medicare once used a beneficiary’s Social Security number to file claims. But the Medicare program loses billions of dollars to fraud every year, and using a person’s Social Security number makes it easier for people who commit fraud to steal identities and abuse Medicare benefits. 

To help remedy the problem of Medicare fraud, the Centers for Medicare & Medicaid Services (CMS) sent new Medicare cards to all beneficiaries in 2018. On the new cards, the Social Security number was replaced by the Medicare claim number to help better protect the identity of each beneficiary and make it harder for someone to commit fraud. 

How your Medicare claim number is used

Medicare beneficiaries generally do not have to file claims on their own. When you receive care, your health care provider will take your Medicare card and use the claim number on the front of your card to file a claim on your behalf. According to Medicare rules, health care providers have one year from the date of service to file a claim. 

If for some reason you must file a Medicare claim yourself, you must complete the Patient Request for Medical Payment (CMS-1490S) along with an itemized bill for your services or items and a letter detailing the reason for filing the claim yourself. 

These documents must be submitted to the appropriate Medicare Administrative Contractor (MAC). These are private health care insurers that have jurisdiction for processing Medicare claims in their respective geographic areas. 

You may call 1-800-MEDICARE (1-800-633-4227) for assistance filing a claim. 

Once your claim is filed, you may track it online in your account within 24 hours of filing. You will also receive a Medicare Summary Notice in the mail every three months detailing all your claims for that period.

How to replace your Medicare card

Call 1-800-MEDICARE (1-800-633-4227) and follow the automated prompts for reporting and replacing a lost or stolen card. You may also print a temporary copy of your card through your account. 


About the author

Christian Worstell is a licensed insurance agent and a Senior Staff Writer for He is passionate about helping people navigate the complexities of Medicare and understand their coverage options.

His work has been featured in outlets such as Vox, MSN, and The Washington Post, and he is a frequent contributor to health care and finance blogs.

Christian is a graduate of Shippensburg University with a bachelor’s degree in journalism. He currently lives in Raleigh, NC.

Where you've seen coverage of Christian's research and reports:

MarketWatch logo

Yahoo Finance logo 


WebMD Logo

South Florida Sun Sentinel Logo Logo

Deseret News Logo

Healthcare Finance Logo