What your denial codes mean — and how to appeal them
A plain-English reference for the most common CARC denial codes. What each one means, why it happens, and the strategy that actually overturns it.
Not deemed a medical necessity
The payer determined the service was not medically necessary based on the diagnosis submitted and their coverage policy. It is one of the most common — and most overturnable — denials when the clinical documentation actually supports the service.
How to appeal CO-50 →Precertification / authorization absent
Precertification, authorization, or notification was required for this service and the payer has no record of it. A leading cause of lost revenue — and frequently recoverable with a retro-auth request or a medical-necessity argument.
How to appeal CO-197 →Claim lacks information or has a billing error
The claim is missing information or contains a submission error. CO-16 almost always travels with a RARC (remark code) that pinpoints the exact missing element — fix it and resubmit.
How to appeal CO-16 →Bundled into another service
The benefit for this service is considered included in the payment for another procedure performed the same day. Often correct — but frequently a missing-modifier issue where a distinct, separately payable service was bundled in error.
How to appeal CO-97 →Diagnosis inconsistent with the procedure
The diagnosis reported is inconsistent with the procedure billed. Usually a coding linkage error rather than a true coverage problem — and quick to overturn when the records support the correct pairing.
How to appeal CO-11 →May be covered by another payer (COB)
Per coordination-of-benefits rules, the payer believes another insurer is primary. Common when COB information is stale — easily resolved once the correct payer order is established.
How to appeal CO-22 →Timely filing limit expired
The claim was received after the payer's filing deadline. Recoverable when you can prove the claim was actually submitted on time — or that a payer error caused the delay.
How to appeal CO-29 →Information doesn't support this many services
The payer says the submitted information doesn't justify the number or frequency of services billed. Overturnable when documentation supports the units.
How to appeal CO-151 →Not covered by this payer or contractor
The claim isn't payable by the payer or contractor it was sent to — often a routing problem (wrong plan, wrong MAC) rather than a coverage decision.
How to appeal CO-109 →Procedure inconsistent with the modifier
The procedure code is inconsistent with the modifier used, or a required modifier is missing. A coding correction that resolves quickly with the right modifier and documentation.
How to appeal CO-4 →Duplicate claim or service
The payer flagged this claim as a duplicate of one already adjudicated. Often a false positive — the same service was billed twice by mistake, or a corrected/resubmitted claim was not recognized as different from the original.
How to appeal CO-18 →Coverage terminated
The patient's insurance coverage was not in effect on the date of service. Appealable when coverage was actually active and the termination data is wrong, or when a retroactive enrollment applies.
How to appeal CO-27 →Charge exceeds fee schedule / maximum allowable
The charge exceeds the contracted fee schedule or the payer's maximum allowable amount. In most cases this is a contractual write-off, not an error — but appeal when the code was miscategorized or the wrong fee schedule was applied.
How to appeal CO-45 →Non-covered charge
The service is not covered under the patient's benefit plan. Sometimes a true benefit exclusion, but frequently a coverage determination that can be challenged with clinical documentation or a different code.
How to appeal CO-96 →Diagnosis is not covered
The diagnosis code submitted is not covered under the patient's plan or is not a covered indication for the service. Often a specificity or selection issue — a more specific or correct ICD-10 code resolves the denial.
How to appeal CO-167 →Provider not certified / credentialed for this plan
The claim was denied because the provider is not enrolled or credentialed with the payer for the service billed. Frequently a credentialing lag — the provider is in-network but processing hasn't completed.
How to appeal CO-B7 →Deductible amount — patient responsibility
The amount reflects the patient's unmet deductible and is properly the patient's responsibility. This is usually correct, but can be wrong if deductible accumulation data is stale or if a secondary payer should cover it.
How to appeal PR-1 →Coinsurance amount — patient responsibility
The amount is the patient's coinsurance percentage per their benefit plan. Correct in most cases — review only if the wrong plan type or benefit tier was applied.
How to appeal PR-2 →Co-payment amount — patient responsibility
The amount is the patient's required copay per their plan. Generally correct and collectible from the patient — only appeal if the visit type (e.g., PCP vs. specialist) was incorrectly categorized.
How to appeal PR-3 →This decision was based on the information available at the time of review
RARC N-115 is an informational remark code indicating the payer made the coverage or medical-necessity decision with the documentation on file at the time of review. It signals that additional supporting information could change the outcome.
How to appeal N-115 →Consult your plan's medical policy for coverage criteria
RARC N-130 directs the provider to the payer's published medical policy for the coverage criteria applicable to this service. It usually accompanies a medical necessity or coverage denial and signals that the appeal must directly address those policy criteria.
How to appeal N-130 →Resubmit with the explanation of benefits from the primary payer
RARC N-522 is an informational code from a secondary payer indicating the claim cannot be processed without the primary payer's explanation of benefits (EOB). This is a documentation issue, not a true denial — attaching the primary EOB resolves it.
How to appeal N-522 →Procedure inconsistent with the patient's age
The procedure billed is inconsistent with the patient's age based on the payer's coverage rules. Often a data entry error (wrong date of birth) or a legitimate age-related coverage limit that can be appealed with supporting clinical rationale.
How to appeal CO-55 →Payment denied when performed by the same or similar provider
The payer denied payment because the service was rendered by the same provider (or a provider in the same group/specialty) as another service billed the same day, triggering a global or mutual-exclusivity edit. Often overturnable with documentation that the services were distinct.
How to appeal CO-57 →See what you're leaving on the table — free
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