Coding and Billing

Why You Need to Use MBIs If You Want to Get Paid

By Mark Wright, OD, FCOVD,
and Carole Burns, OD, FCOVD

Jan. 5, 2022

We realized recently that we had overlooked an important topic in coding and billing: Medicare Beneficiary Identifiers (MBIs).

In April 2018, Medicare removed Social Security Numbers (SSN) from Medicare cards and replaced them with Medicare Beneficiary Identifiers (MBIs). Here’s what the new card looks like:i

Social Security Numbers were created in 1936. They were created to keep track of the earnings history of U.S. workers for Social Security entitlement and benefit computation purposes. Over time the use of the number has evolved. Today, the Social Security Number has come to be used as a nearly universal identifier. A Social Security Number is assigned at birth and follows an individual their entire lives.

Can I refuse to give my Social Security number to a private business?
“Anyone can refuse to disclose his or her number, but the requester can refuse its services if you do not give it. Businesses, banks, schools, private agencies, etc., are free to request someone’s number and use it for any purpose that does not violate a federal or state law. Sometimes they will issue a different number if you ask.”ii

Be vigilant about giving out your Social Security Number. Don’t automatically give it out when asked. When in doubt, you can:
• Ask the name of the law which requires the organization to collect it and for an explanation of that law.
• Request an identification number that is not your SSN.
• Ask to have your identity verified by another means.
• Inquire what measures and procedures are in place to keep your number safe. Is it stored on portable devices, especially ones that leave the office? Is it encrypted? Which staff members have access to it, and do they need access to perform their duties? If the SSN is on paper, is the paper shredded and how secure is that paper before it is shredded?
• Refuse to give it out. Be aware, however, companies and other organizations can elect to not provide you service if you refuse.iii

Treat Social Security numbers and MBIs as Protected Health Information (PHI).

Why did Medicare change from using SS numbers to MBIs?
Medicare is changing from using Social Security Numbers to MBIs to protect the identities of people with Medicare and keep them safer from identity theft. This change is only for Medicare. It does not mean that you do not have to use your Social Security Number for other reasons like reporting to the Social Security Administration or the Internal Revenue Service.

When does a provider need to use an MBI?
Use MBIs for all Fee-For-Service (FFS) claims submissions with:
• Dates of service before the MBI change date – use old or new MBIs
• Span-date claims with a “From Date” before the MBI change date – use old or new MBIs
• Dates of service that are entirely on or after the effective date of the MBI change – use new MBIs

What to do if the patient’s MBI number changes?
Medicare beneficiaries or their authorized representatives can ask to change their MBIs. As an example, if the MBI is compromised a new number can be issued. CMS can also change an MBI. If a patient seeks care before getting a new card with the new MBI you may get a HIPAA Eligibility Transaction System (HETS) eligibility transaction error code (AAA 72) of “invalid member ID.” (By going to, anyone is able to see information regarding Medicare and Medicaid services. This website also provides the ability to utilize the HETS service.)iv

Here’s what to do:
• Do a historic eligibility search to get the termination date of the old MBI.
• Get the new MBI from your Medicare Administrative Contractor’s secure MBI look-up tool. Sign up (PDF) for the Portal to use the tool.

When communicating with beneficiaries, use the term “Medicare Number.” Avoid using the terms “HICN” and “MBI.”v

i. The Story of the Social Security Number (
ii. KA-02232 · Customer Self-Service (
iii. Who Needs Your Social Security Number? (And When to Refuse to Give it Out) – Money Care (
iv. HETS Status – hetsstatus
v. SSA – POMS: HI 00901.040 – New Medicare Numbers and Number Change Requests – 07/28/2021

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