CO-96
Depends on the detailsNon-covered charge(s)
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-96 is a broad 'non-covered charge' code. On its own it doesn't tell you why the charge wasn't covered — it almost always appears with a Remittance Advice Remark Code (RARC), typically starting with N or M, that gives the real reason.
Because it's a Contractual Obligation (CO), the provider generally can't bill you for it. To do anything useful with a CO-96, you first need to read the accompanying remark code, since that's what determines whether and how to appeal.
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Why you're seeing CO-96
- The service is excluded under the plan (the remark code will say so).
- A required modifier, document, or piece of information was missing.
- The service was bundled into another payment.
- The care fell outside a covered benefit category.
Can you appeal it?
It entirely depends on the paired remark code — find that code first, then decide whether an appeal or a billing correction is the right move.
What to do next
- 1Find the Remittance Advice Remark Code (RARC) printed next to CO-96 on the EOB.
- 2Look up what that specific remark code means — it's the real reason for the denial.
- 3If the remark points to a fixable billing issue, ask the provider to correct and resubmit.
- 4If it points to a coverage or necessity decision, appeal that underlying reason in writing.
Evidence that helps
- The full EOB showing the remark code paired with CO-96.
- Documentation that rebuts the specific remark-code reason.
Frequently asked questions
Why doesn't CO-96 explain the denial?
CO-96 is intentionally generic — it just says 'non-covered.' The specific reason is in the accompanying remark code (usually an N- or M- code) on the same EOB. Always read that remark code first.
Can I be billed for CO-96?
Because it's a 'CO' (contractual obligation) code, the provider generally can't bill you. If you're being billed anyway, ask the provider to explain under which contract term they believe you're responsible.
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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.
- U.S. Department of Labor — ERISA claims & appeals
Governs claim and appeal procedures and deadlines for most employer-sponsored (ERISA) health 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.