CO-97
Depends on the detailsPayment bundled into another service
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-97 means the payer considers this service to be included in the payment for another procedure billed the same day — so it isn't reimbursed separately. This is a bundling decision based on coding rules.
It's a Contractual Obligation (CO), so you generally can't be billed. Whether it's correct depends on the coding: sometimes a service genuinely is bundled, and sometimes a missing modifier caused two legitimately separate services to be merged.
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Why you're seeing CO-97
- The service is normally included in a related procedure under bundling (NCCI) rules.
- A modifier that would identify it as a separate service was missing.
- Two procedures were billed together that the payer treats as one payment.
Can you appeal it?
Appealable when the services were genuinely distinct and a modifier or documentation supports separate payment — often a provider coding fix.
What to do next
- 1Ask the provider's billing office whether a modifier was needed to unbundle the services.
- 2Confirm whether the two services were genuinely separate and separately documented.
- 3If so, have the provider resubmit with the correct modifier and documentation.
- 4Appeal if the payer refuses to recognize a legitimately separate service.
Evidence that helps
- Operative or procedure notes showing the services were distinct.
- Coding guidance supporting a modifier for separate payment.
Frequently asked questions
What does 'bundled' mean?
It means the payer treats one service as already included in the payment for another related service performed the same day, so it isn't paid on its own. This follows national coding (NCCI) edits.
Can a CO-97 be appealed?
Yes, when the services were genuinely separate. Often the fix is a corrected claim with the right modifier and supporting documentation rather than a formal appeal.
Related guide: How to appeal a “Billing or coding error” 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.