CMS Pub. 100-04, ch. 2, § 30.1

The term Medicare beneficiary identifier (Mbi) is a general term describing a

beneficiary's Medicare identification number. For purposes of this manual, Medicare

beneficiary identifier references both the Health Insurance Claim Number (HICN) and

the Medicare Beneficiary Identifier (MBI) during the new Medicare card transition

period and after for certain business areas that will continue to use the HICN as part of

their processes.

If a beneficiary’s entitlement to Medicare has been transferred from one Medicare

beneficiary identifier to another, the CWF will cross-reference the old number to the new

number. If there has been utilization of benefits under each number, all data will be

combined under the new number.

A. Disposition Code 51

1. If, after submitting the admission notice or Part B claim to CMS, the MAC receives

a disposition code of 51 with trailer code 01 containing a possible Medicare

beneficiary identifier, the MAC investigates the new Medicare beneficiary

identifier, and if it believes the new Medicare beneficiary identifier is correct, the

MAC resubmits the claim under the new Medicare beneficiary identifier. CWF

responds with an appropriate disposition code and any associated trailers for

processing the claim.

2. If the MAC receives a disposition code of 51 without trailer code 01, or after

investigation determines the Medicare beneficiary identifier in the 01 trailer is

incorrect, it denies the claim using the following message:

Payment cannot be made for the services you received from (name

of provider) because we have no record of your Medicare

beneficiary identifier. Please write your correct number on the

claim and resubmit the claim to (name of provider). If you think

the number is right, check with your local Social Security Office.

B. Disposition Code 55

If CWF returns disposition code 55 and trailer code 08 containing an error code of 5052,

indicating a mismatch in the beneficiary’s personal characteristics, CWF will also return

to the MAC what it believes to be the proper information on trailer code 10. The header

portion of the response also contains the corrected sex and birth date, if applicable, of the

beneficiary.

The MAC investigates the information provided, corrects the information on the claim,

and resubmits it to CWF. If the MAC continues to receive a code 55, it contacts the Host

through locally established procedures. See Chapter 27.