CO-22
Often appealableMay be covered by another payer (coordination of benefits)
Group CO — Contractual Obligation — an adjustment tied to the contract between the insurer and the provider. You usually cannot be billed for a CO amount.
CO-22 means this care may be covered by another payer under coordination-of-benefits (COB) rules — the insurer believes a different plan is primary and should pay first. It's common when you have more than one coverage source.
It's usually resolved by confirming which plan is primary and updating the insurers' COB records, then having the claim processed in the correct order.
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Why you're seeing CO-22
- You have two or more health plans and the primary payer wasn't billed first.
- The insurer's coordination-of-benefits information is outdated.
- Another coverage type (auto, workers' comp, or liability) may be responsible.
Can you appeal it?
Typically fixed by updating COB information and billing the primary payer first, rather than a formal appeal.
What to do next
- 1Confirm which of your plans is primary under coordination-of-benefits rules.
- 2Update the coordination-of-benefits information with both insurers.
- 3Have the claim submitted to the primary payer first, then the secondary with the primary's EOB.
- 4Appeal if the insurer is wrong about another payer being responsible.
Evidence that helps
- Details of all your active coverage and effective dates.
- The primary payer's EOB when billing a secondary plan.
Frequently asked questions
What is coordination of benefits?
When you're covered by more than one plan, coordination of benefits decides which plan pays first (primary) and which pays second (secondary). CO-22 usually means the claim needs to go to the primary payer first.
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Other common denial codes
Last reviewed July 18, 2026. Denial-code lists (CARC/RARC) are updated three times a year; we review these explanations against the current list.
Sources & references
These explanations are written in plain language and based on the authoritative sources below. Always confirm the specifics against your own plan documents and denial letter.
- ASC X12 — Claim Adjustment Reason Codes (CARC)
The standards body that maintains the official CARC list (the CO/PR codes), updated three times a year.
- CMS / X12 — Remittance Advice Remark Codes (RARC)
The remark codes (N-/M- codes) that accompany a CARC and give the specific reason for an adjustment.
- HealthCare.gov — Appealing a health plan decision
Official overview of internal appeals and external review rights for Marketplace and most private plans.
- Your state's insurance regulator
State agencies enforce external review and consumer protections; find yours via the NAIC directory.
Important: this is not legal or medical advice.
AppealBrain is a free, self-help tool that helps you draft an appeal letter using the information you provide. We are not a law firm, medical provider, or insurance company, and using this tool does not create an attorney–client relationship. Appeal rules and deadlines vary by plan and state — always review your own denial letter and plan documents, and consider consulting a licensed professional for your specific situation. We do not guarantee any outcome.