Coordination of Benefits (COB)
Coordination of Benefits
The rules and processes that determine which of two or more insurance plans pays first when a patient is covered by multiple plans.
1 min read · Last reviewed May 23, 2026
At a glance
- Category
- Payer
- Acronym for
- Coordination of Benefits
- Primary sources
- 2
- Workspace handoff
- denial workbench →
Where this comes up
Front-office and billing both hit this term — eligibility before the visit, prior auth before the procedure, contract terms during fee-schedule negotiation, and credentialing whenever a new provider joins or a payer roster lapses. Misses here become denials downstream.
Full definition
What it is in practice
CMS COB coordinates Medicare with other payers. Commercial COB follows model state regulations adopted by most states.
How it shows up in your practice
Verify COB at every registration. Eligibility tools (270/271) typically expose primary/secondary status.
Sources
- CMS — Medicare Secondary Payerhttps://www.cms.gov/medicare/coordination-benefits-recovery/medicare-secondary-payer
- CMS — HIPAA Administrative Simplificationhttps://www.cms.gov/regulations-and-guidance/administrative-simplification
Resolve COB denials in the Denial Workbench
Open denial workbench →Related terms
- Denials & AppealsMedicare Secondary Payer (MSP)Statutory rules at 42 USC 1395y(b) requiring other insurance to pay before Medicare in defined situations.
- Payer270/271 Eligibility Inquiry/ResponseThe HIPAA standard EDI transactions used to verify patient insurance eligibility (270 query, 271 response).
- 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.
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.
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Related across the archive
- Glossary270/271 Eligibility Inquiry/ResponseThe HIPAA standard EDI transactions used to verify patient insurance eligibility (270 query, 271 response).
- GlossaryMedicare Secondary Payer (MSP)Statutory rules at 42 USC 1395y(b) requiring other insurance to pay before Medicare in defined situations.
- GlossaryOA (Other Adjustment)An X12 adjustment group code used when no other group code applies — frequently for coordination of benefits and other payer adjustments.
- 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.
- Glossary835 Electronic Remittance Advice (ERA)The HIPAA-mandated electronic transaction by which payers communicate payment and adjustment information to providers.
- Glossary837 Electronic ClaimThe HIPAA-mandated electronic transaction for submitting professional (837P), institutional (837I), or dental (837D) claims.
- ComplianceOIG LEIE Monthly Exclusion Screening: Process + Audit-Ready LogsMonthly OIG LEIE and SAM.gov exclusion screening for every workforce member and vendor: the workflow, the log fields auditors require, and the escalation path.
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.