CO-197
Often appealablePrecertification / prior authorization not obtained
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-197 means your plan required advance approval — precertification, prior authorization, or pre-notification — for the service, and the insurer says that approval wasn't obtained before the care was provided. Because it's grouped as a Contractual Obligation (CO), the provider generally cannot bill you for this amount, but the claim itself is unpaid until the authorization issue is resolved.
This is an administrative denial about a missing approval step — not a decision that your care was unnecessary. That distinction is why CO-197 is one of the more winnable denials, especially when the care was urgent or the requirement wasn't clearly communicated.
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Why you're seeing CO-197
- The provider's office didn't submit an authorization request before the service.
- An authorization existed but expired, or didn't match the final procedure code that was billed.
- The care was urgent or emergent and there was no time to obtain approval in advance.
- The prior-authorization requirement wasn't clearly communicated to you or your provider.
Can you appeal it?
Frequently reversible — many plans allow retroactive authorization when the care was covered and necessary, particularly for urgent situations.
What to do next
- 1Confirm in writing whether an authorization was ever requested and what its status is.
- 2Ask your provider's office to submit or resubmit the authorization retroactively if the plan allows it.
- 3Document any urgency or lack of notice that made advance approval impractical.
- 4File a written appeal asking for retroactive authorization and reprocessing of the claim before your deadline.
- 5If it's upheld, request external review and ask which plan provision permits denying necessary care solely for a missing authorization.
Evidence that helps
- The referral or order from your treating provider.
- Proof the care was urgent or time-sensitive, if applicable.
- Any communications (or lack of them) about the authorization requirement.
Frequently asked questions
Can I be billed for a CO-197 denial?
Generally no. The 'CO' group means it's a contractual obligation between the plan and the provider, so the provider typically can't bill you for it. But the claim stays unpaid until the authorization issue is resolved, so it's still worth appealing.
Is CO-197 worth appealing?
Often, yes. Because it's an administrative denial about a missing approval — not a decision that your care was unnecessary — many plans will grant authorization retroactively, especially when the care was urgent or the requirement wasn't clearly communicated.
Who was supposed to get the prior authorization?
Usually the provider's office submits the request, but you can confirm it was done. If it was missed, ask them to submit it retroactively while you file your appeal.
Related guide: How to appeal a “Prior authorization issue” denial →
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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.