Denial code library
Every claim adjustment reason code your payers send, in plain English — what it means, why it happened, how to work it, and how to stop it from coming back. Written for billing teams, not for a code book.
All codes
Deductible amount
The service was covered, but the amount fell within the patient’s unmet annual deductible, so the plan paid nothing toward it and the balance moves to the patient.
Coinsurance amount
The plan paid its share of the allowed amount and this is the patient’s percentage share — a normal covered-claim outcome, not a denial.
Co-payment amount
A flat per-visit copay defined by the plan. The claim was covered; this fixed dollar amount belongs to the patient.
Procedure code inconsistent with modifier / modifier missing
The payer could not adjudicate the line because the modifier on it contradicts the procedure code, or a modifier the code requires was not submitted.
Procedure code inconsistent with place of service
The place of service on the claim is not one where the payer permits that procedure to be performed and billed.
Procedure inconsistent with patient age
The billed code carries an age restriction that the patient’s date of birth on the claim does not satisfy.
Procedure inconsistent with provider type / specialty
The payer does not recognise the billing or rendering provider’s specialty as eligible to perform and bill that procedure.
Diagnosis inconsistent with patient age
The diagnosis submitted carries an age restriction that the patient’s date of birth does not satisfy.
Diagnosis inconsistent with procedure
The diagnosis code linked to the service does not support that procedure under the payer’s coverage rules.
Authorization number missing or invalid
An authorization was required and one was obtained, but the number submitted does not match what the payer has on file for these services or this provider.
Claim lacks information for adjudication
Something required to process the claim is missing or malformed — the accompanying remark codes name the specific field.
Exact duplicate claim or service
The payer already has a claim for this patient, provider, date, and service on file and will not adjudicate it a second time.
Care may be covered by another payer
The payer believes another plan is primary and wants that plan to adjudicate first.
Impact of prior payer adjudication
A secondary payer is reporting the effect of what the primary already paid — informational, not a denial.
Expenses incurred prior to coverage
The date of service falls before the patient’s coverage under this plan began.
Expenses incurred after coverage terminated
The patient’s coverage under this plan had ended before the date of service.
Timely filing limit exceeded
The claim reached the payer after its filing deadline, so it will not be adjudicated — and in most contracts the balance cannot be billed to the patient.
Patient cannot be identified as our insured
The payer cannot match the patient on the claim to any member in its system.
Charge exceeds fee schedule / maximum allowable
The billed charge was above the contracted allowed amount, and the difference is a contractual write-off — not a balance you may bill the patient.
Routine or preventive service not covered
The plan does not cover the routine or screening service billed, or does not cover it at the frequency submitted.
Not deemed a medical necessity
The payer decided the documentation and coding do not establish that the service was medically necessary under its coverage policy.
Multiple physicians or assistants not covered
The payer will not separately reimburse an additional surgeon, assistant, or co-provider for this procedure.
Experimental or investigational
The payer classifies the service as investigational and excludes it from coverage under the plan.
Processed under multiple or concurrent procedure rules
Payment was reduced because more than one procedure was performed in the same session and the payer applied a multiple-procedure discount.
Plan procedures not followed
A procedural requirement of the plan — referral, notification, network routing — was not satisfied before the service.
Non-covered charge(s)
The service is not a benefit under this plan — the remark codes explain which exclusion applies.
Service bundled into another payment
The payer considers this service part of another service already paid, so it carries no separate payment.
Not covered by this payer — send to the correct payer
The claim went to the wrong payer or the wrong contractor entirely and needs to be routed elsewhere.
Benefit maximum reached
The patient has used up the plan’s limit for this benefit — visits, units, dollars, or occurrences — for the period.
Patient ID number and name do not match
The member ID and the patient name on the claim point to different people in the payer’s records.
Information does not support this many services
The number of units or the frequency billed exceeds what the payer’s policy or the submitted documentation supports.
Diagnosis not covered
The plan excludes the diagnosis submitted, so no service billed against it will be covered.
Payment denied for this provider type
The payer does not reimburse this service when it is billed by a provider of this type.
Patient has not met eligibility requirements
The patient did not satisfy a condition the plan requires before this benefit becomes available.
Procedure code invalid on the date of service
The procedure code did not exist or was no longer active on the day the service was performed.
Procedure modifier invalid on the date of service
The modifier submitted was not valid, or not valid with that code, on the date the service was performed.
Referring provider not eligible to refer
The provider listed as referring is not enrolled, not eligible, or not correctly identified for referrals with this payer.
Precertification / authorization absent
The service required prior authorization and none was obtained before it was rendered.
Not covered under the patient’s current benefit plan
The specific service is excluded from this patient’s plan, even though the patient has active coverage.
Services not provided by network providers
The rendering provider was out of network for this plan, so the service was denied or reduced under the network benefit.
Attachment or documentation required
The payer needs supporting documentation it does not have before it will finish adjudicating the claim.
Claim or service denied — see remark codes
A generic denial whose real reason lives entirely in the accompanying remark codes.
Provider not certified or eligible for this service
The provider’s enrolment or certification with the payer did not cover this service on the date it was performed.
Common questions
What is a CARC code?
A claim adjustment reason code (CARC) is the standardised code a payer includes in an 835 remittance file to explain why it adjusted or denied part of a claim. It is always paired with a group code — CO for contractual obligation, PR for patient responsibility, OA for other adjustment, or PI for payer-initiated reduction — which determines who is financially responsible for the amount.
What is the difference between a CARC and a RARC?
A CARC states the category of the adjustment; a RARC (remittance advice remark code) adds the specific detail. For broad codes such as CO-16, the CARC alone is not actionable and the remark code carries the real reason — which is why denial reporting that captures only reason codes cannot resolve its largest denial category.
What does the CO, PR, or OA prefix mean?
The prefix is the group code and it assigns financial responsibility. CO means the provider absorbs the amount as a contractual obligation and cannot bill the patient. PR moves the amount to the patient. OA covers other adjustments, commonly coordination of benefits. PI is a payer-initiated reduction the provider is not permitted to pass on.
Which denial codes cost practices the most?
By recoverable dollars, prior authorization (CO-197), medical necessity (CO-50), and timely filing (CO-29) are consistently the most expensive — the first two because the amounts are large and the appeals are winnable, and the third because the revenue is usually unrecoverable once the window closes.
Stop looking codes up one at a time
PayerVista reads the 835 remittance files your payers already send and groups every denial by reason, payer, and dollar impact — so you see which codes are actually costing you, instead of decoding them claim by claim.
Claim adjustment reason codes are maintained and periodically revised by X12, the standards body that publishes the underlying EDI transactions. The descriptions here are a plain-English reference, not the official code text, and payer policy varies — always confirm against your payer agreement and the remark codes on the remittance itself.