Crossover claims: Supplemental insurance and Medigap plans

The Coordination of Benefits Agreement (COBA) Medicare claims crossover program establishes a nationally standard contract between CMS and other health insurance organizations that defines the criteria for transmitting enrollee eligibility data and Medicare adjudicated claim data to supplemental payers. A national claims crossover contractor, MSP contractor, administers Medicare claims crossover functions on CMS' behalf.

If the insurer has a COBA with Medicare, Medicare will cross over the claim information to the insurer. An eligibility file is sent from the Trading Partner (supplemental insurance/Medigap plan) to the MSP contractor. The file contains data to identify the Medicare ID and claims criteria, specified by the Trading Partner, for crossovers. Each Trading Partner is issued a COBA ID. The COBA ID and eligibility file data, along with information specific to that trading partner, are stored in CWF. When claims are processed, CWF compares each COB trading partner's claims selection criteria against the Medicare claims. If the claim matches the trading partner's claims criteria and Medicare ID in their eligibility file, the claim information is automatically crossed over to the trading partner, via an electronic file. For more information, visit the COBA webpage. This webpage also provides the current list of automatic crossover Trading Partners with a COBA.

Virtually all standard Medigap plans, defined in Section 1882(g)(1) of Title XVIII of the Social Security Act, participate in the automatic or eligibility file-based crossover process. Such plans typically accept institutional as well as professional Medicare crossover claims from Medicare daily. Approximately ten or eleven Medigap plans avail themselves of the less commonly used Medigap claim-based crossover process, which cannot be used in association with Part A 837 institutional claims (including inpatient, outpatient, home health, and hospice related types of bills) or with claims for which the physician or supplier is non-participating with Medicare.

Note: If your claim was not electronically crossed over, please contact the supplemental or Medigap insurance for further instructions.

Identifying crossover claims on the electronic remittance advice (ERA)

The crossover information can be found on the ANSI 835 ERA in the "TRANSFER TO (COB)" field. The Trading Partner's ID will be located in the "ID CODE" field on the ERA. If the claim crossed over to multiple Trading Partners, only the first one will be listed on the ERA.

Identifying crossover claim in the Fiscal Intermediary Standard System (FISS)

The payment section, on page six of FISS, contains a "CROSSOVER IND" field. This field will either be blank or have a value of 1 in it. If it is blank, the claim did not cross over. If it contains a "1", the claim did cross over to the Trading Partner in the field titled "PARTNER ID". The Trading Partner ID is a nine-digit ID assigned by COBC. The payment data section in DDE (claim pg. 06) will indicate the same fields as mentioned above, "CROSSOVER IND" and "PARTNER ID". 

Medigap claim-based crossover process

The term Medigap refers to Medicare supplemental insurance. It is private health insurance designed specifically to supplement Medicare benefits by filling in some of the gaps in Medicare coverage by providing payment for some of the charges for which Medicare does not have responsibility due to the applicability of deductibles, coinsurance amounts, or other limitations imposed by Medicare.

Note: For specific supplemental and/or Medigap coverage information, please contact the supplemental or Medigap insurer.

For participating providers, when reporting Medigap claim-based information, report the following on the CMS-1500 claim form or electronic equivalent.

Reporting requirements for Medigap information are:

• Group policy number
• Medigap/Insurer ID code

Medicare will automatically advise the Medigap insurer of Medicare's approved amount and payment for the billed services. The Medigap insurer can then determine their liability and make payment to the participating provider. This "one-step" billing eliminates the need for you to submit a separate bill to the patient or their Medigap insurer after receiving Medicare's payment.

For additional information for placement of Medigap information on the claim form, please refer to the CMS-1500 (02/12) data element requirements.
 

References

• COBA Trading Partners
• COBA Trading Partners Customer Service Contacts - March 2026 (list of automatic crossover Trading Partners in production)