CMS Pub. 100-05, ch. 6, § 10

A/B Medicare Administrative Contractors (MACs) (Part A), A/B MACs (Part B), or A/B

MACs (Part HHH) (collectively referred to as A/B MACs) and Durable Medical

Equipment MACs (DME MACs) obtain information pertinent to the identification of

MSP for each beneficiary via the CWF, MSP auxiliary file. The auxiliary file is

associated with the beneficiary's master record within CWF.

The MSP Contractor completes MSP updates on a daily basis upon receipt of notice that

another payer is primary to Medicare (e.g., an explanation of benefits, a beneficiary

questionnaire, a notice from a third-party payer, Section 111 reporting, etc.). Every claim

for a given beneficiary is validated against the same MSP data housed in a CWF, MSP

auxiliary file, thus permitting uniform processing. Contractor claims data inconsistent

with a CWF, MSP auxiliary file will cause rejects and/or error conditions. An MSP

auxiliary record consistent with an identified MSP situation must be present before a

payment is approved for an MSP claim. An MSP auxiliary record is established by an

MSP maintenance transaction submitted to CWF. The claim must agree with the MSP

auxiliary record that was established, or it will not process.

The MSP Contractor is the source for establishing new MSP records, with the exception

of four situations described in §10.1, below. The MSP Contractor submits MSP

maintenance transactions on the basis of information obtained outside the claims process.

Examples include, voluntary MSP insurer data match agreements, MMSEA Section 111

reporting, attorney, beneficiary, provider information, and 411.25 Notices.