Medicare Secondary Payer (MSP)
Medicare Secondary Payer
Statutory rules at 42 USC 1395y(b) requiring other insurance to pay before Medicare in defined situations.
1 min read · Last reviewed May 23, 2026
At a glance
- Category
- Denials & Appeals
- Acronym for
- Medicare Secondary Payer
- Primary sources
- 1
- Workspace handoff
- denial workbench →
Where this comes up
This is denial-workbench territory. A remit posts with a CARC/RARC, the biller decides whether to rebill, appeal, or write off, and the appeal packet has to cite the chart, the order, and the payer's own policy language. Recurring patterns trace back to an upstream workflow gap.
Full definition
What it is in practice
CMS MSP defines situations where Medicare is secondary: working aged, ESRD coordination, no-fault, liability, workers' comp, group health for disabled. The MSP questionnaire at registration captures the data needed to route claims correctly.
How it shows up in your practice
Update MSP at each registration. Misrouted primary/secondary claims drive predictable denials and recoupments.
Sources
- CMS — Medicare Secondary Payerhttps://www.cms.gov/medicare/coordination-benefits-recovery/medicare-secondary-payer
Resolve MSP denials in the Denial Workbench
Open denial workbench →Related terms
- PayerCoordination of Benefits (COB)The rules and processes that determine which of two or more insurance plans pays first when a patient is covered by multiple plans.
- Denials & AppealsOA (Other Adjustment)An X12 adjustment group code used when no other group code applies — frequently for coordination of benefits and other payer adjustments.
- Denials & AppealsDenial ManagementThe end-to-end workflow of identifying, categorizing, appealing, and preventing claim denials.
D3rx is a healthcare-billing and compliance research aid maintained by D3rx Inc. Articles are drafted by an LLM (Anthropic Claude) against primary HHS, OCR, CMS, eCFR, NIST, and state-regulator publications, and reviewed for restraint and source fidelity by the D3rx team.
Reviewer status: a named credentialed reviewer (CHC, CHPC, or healthcare attorney) is being engaged. Until that engagement is finalized, this page does not claim credentialed review.
Related across the archive
- GlossaryOA (Other Adjustment)An X12 adjustment group code used when no other group code applies — frequently for coordination of benefits and other payer adjustments.
- GlossaryCoordination of Benefits (COB)The rules and processes that determine which of two or more insurance plans pays first when a patient is covered by multiple plans.
- GlossaryDenial ManagementThe end-to-end workflow of identifying, categorizing, appealing, and preventing claim denials.
- GlossaryDual-EligibleAn individual enrolled in both Medicare and Medicaid.
- GlossaryQMB (Qualified Medicare Beneficiary)A category of dual-eligible whose Medicare cost-sharing (deductibles, coinsurance, premiums) is paid by Medicaid.
- BillingHow to Appeal an Insurance Denial: Step-by-Step GuideClaim denied? Step-by-step appeal process with payer deadlines, denial code fixes, appeal letter template, and escalation options.
- BillingMedical Billing Denial Codes: What They Mean and How to Fix ThemCO-4, CO-97, CO-16, PR-96 and more. What each denial code means and exactly how to fix it.
- Glossary835 Electronic Remittance Advice (ERA)The HIPAA-mandated electronic transaction by which payers communicate payment and adjustment information to providers.
This glossary entry is a research aid for billing and compliance staff. It does not provide legal, medical, or financial advice and does not replace counsel. References cited link to primary sources at HHS, OCR, CMS, eCFR, NIST, and the relevant payer or industry body.