CMS explains January Medicare Secondary Payer adjustment-code processing
Sep 27, 2026 edition · GC-2026-0031 · Published 2026-09-27 · Version 2 · Final
CMS’s January MSP processing update changes how specified adjustment codes are handled. Providers must preserve the primary payer’s CAS adjustments rather than recoding them to obtain automated processing.
What happened
CMS issued MM14553 on September 4 for the August 21 change request addressing specified Medicare Secondary Payer claim adjustment reason codes. The Part A MAC/FISS changes are effective January 1, 2027, with implementation January 4. Some codes are handled systematically, while others suspend for manual review or deny. MACs may return claims Medicare cannot process and identify the reason on remittance advice, allowing correction and, where appropriate, resubmission to the primary payer or Medicare. A returned claim is not automatically payable after resubmission.
Primary payers and Medicare communicate adjustments through the CAS segment of an 835 remittance or paper advice. Providers must transfer the primary payer’s CAS adjustments unchanged to the 837 institutional claim submitted for Medicare secondary payment. Systems use those amounts and CARCs to calculate payment, so a mapping change should not alter the underlying adjustment merely to force a particular processing route. The January implementation concerns handling of the specified codes; it does not replace accurate coordination-of-benefits reporting.
Scope and timing
- Authority status
- Final
- Applicability
- Operationally relevant
- Audience
- Health systems, Provider networks
- Jurisdiction
- Federal
- Affected functions
- Revenue Cycle, Coding, IT
- Responsible owner
- Revenue Cycle
- Recorded date
- 2027-01-01
- Date type
- effective
Why it matters
Secondary-claim payment depends on preserving the primary payer’s information as well as using the correct processing rules. A technical workaround that changes that information can create a separate accuracy problem.
Recommended action
Map affected CARCs and expected FISS handling, verify unchanged transfer of CAS adjustments and prepare representative tests before January implementation. Route returned or suspended claims using the stated reason rather than assuming they all warrant the same resubmission.
Sources
- MM14553, Medicare Secondary Payer claim processingOfficial · CMS · 2026-09-04 · Source review 2026-09-06
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