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Dental denial code lookup

The 30 CARC codes that hide most of the money on dental remittances. What each one means, whether it is worth appealing, and exactly how.

CO-4High

Procedure code inconsistent with the modifier used, or a required modifier is missing

The payer could not adjudicate the claim because the modifier does not match the procedure code, or a required modifier was left off. On dental claims this usually points to tooth, surface, quadrant, or arch reporting problems rather than true modifier disputes.

How to appeal it
CO-6Medium

Procedure/revenue code inconsistent with the patient's age

The procedure billed conflicts with the patient's age on file, either because the plan limits the service to an age band or because the wrong code variant was billed for the patient's age.

How to appeal it
CO-11Medium

The diagnosis is inconsistent with the procedure

The payer's edits found that the diagnosis code does not support the procedure billed. On dental claims this is most common when billing medical payers or dental plans that require ICD-10 codes on the 837D.

How to appeal it
CO-15Medium

The authorization number is missing, invalid, or does not apply to the billed services or provider

An authorization exists somewhere in the process, but the number on the claim is missing, wrong, expired, or tied to a different service or provider than the one billed.

How to appeal it
CO-16High

Claim/service lacks information or has submission/billing error(s)

The claim is missing information the payer needs to adjudicate it, or contains a submission error. The accompanying remittance advice remark codes specify exactly what is missing.

How to appeal it
CO-18Medium

Exact duplicate claim/service

The payer believes this claim or service line exactly duplicates one already received. Sometimes it truly does; on dental claims it is often two legitimate services that look identical to the payer's automated edits.

How to appeal it
CO-22Medium

This care may be covered by another payer per coordination of benefits

The payer believes another plan is primary for this patient and will not pay until the other payer's adjudication is on file. The dollars are usually recoverable, but only after the coordination of benefits chain is untangled.

How to appeal it
OA-23Low

The impact of prior payer(s) adjudication, including payments and/or adjustments

This code reports how much of the billed amount was already accounted for by a prior payer's payment and adjustments. It appears with group code OA on secondary claims and is informational accounting rather than a true denial.

How to appeal it
CO-26Low

Expenses incurred prior to coverage

The payer's records show the date of service falls before the patient's coverage became effective, so the plan is refusing the entire charge.

How to appeal it
CO-27Low

Expenses incurred after coverage terminated

The payer shows the patient's coverage ended before the date of service. This clusters around job changes and is especially painful on multi-visit dental work completed after the termination date.

How to appeal it
CO-29Medium

The time limit for filing has expired

The claim arrived after the payer's filing deadline, which on dental plans commonly ranges from 90 days to one year from the date of service.

How to appeal it
CO-31High

Patient cannot be identified as our insured

The payer cannot match the patient on the claim to a covered member. This is usually a data problem: wrong subscriber ID, misspelled name, wrong date of birth, or the wrong payer entirely.

How to appeal it
CO-45Low

Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement

The difference between your billed fee and the plan's allowed amount. For in-network dentists this is the contractual write-off: not money the patient owes, and usually not money anyone can recover.

How to appeal it
CO-50Medium

Non-covered services: not deemed a medical necessity by the payer

The payer's reviewer decided the documentation does not establish that the service was necessary. On dental claims this is a documentation fight far more often than a genuine clinical dispute.

How to appeal it
CO-55Low

Procedure/treatment/device deemed experimental or investigational by the payer

The plan classifies the procedure as experimental or investigational and excludes it on that basis, regardless of the clinical result.

How to appeal it
CO-96Low

Non-covered charge(s)

The plan does not cover this service, and the accompanying remark codes name the specific exclusion. Recovery depends on whether the exclusion actually applies to the facts, not on persuading the payer to change the plan.

How to appeal it
CO-97Medium

Benefit included in the payment/allowance for another service already adjudicated

The payer bundled this service into another procedure's payment. Sometimes that is correct under coding rules; on dental claims it frequently overreaches when the services were genuinely distinct.

How to appeal it
CO-109High

Claim/service not covered by this payer/contractor; you must send the claim to the correct payer

You billed a payer that does not hold responsibility for this member or service. The fix is redirection, and speed matters because the correct payer's filing clock has been running the whole time.

How to appeal it
PR-119Medium

Benefit maximum for this time period or occurrence has been reached

The plan has paid out the member's annual or lifetime maximum, so the balance shifts to the patient. It is correct much of the time, but worth checking because accumulator math and plan-year assignments are frequently wrong.

How to appeal it
CO-131Low

Claim specific negotiated discount

An adjustment reflecting a discount negotiated for this specific claim, most often seen on out-of-network dental claims routed through third-party repricing or negotiation vendors.

How to appeal it
CO-151Medium

Payment adjusted because the information submitted does not support this many/frequency of services

The payer says the quantity or frequency billed exceeds what the plan allows or what the documentation supports. Dental plans are dense with frequency limits, so this code does heavy lifting on dental remittances.

How to appeal it
CO-167Medium

This (these) diagnosis(es) is (are) not covered

The plan does not cover services for the diagnosis reported. On dental claims this appears mostly on medically billed dentistry and on plans that require diagnosis codes for specific procedures.

How to appeal it
CO-170Low

Payment is denied when performed/billed by this type of provider

The plan will not pay this provider type for this service. On dental claims this surfaces around hygienists, new associates, and dentists billing medical plans for services the plan reserves for physicians.

How to appeal it
CO-197High

Precertification/authorization/notification/pre-treatment absent

The payer required prior authorization, precertification, or a pre-treatment review before the service and has no record of one. This is among the most appealable denials in dentistry, because retroactive authorization is widely available when clinical necessity is documented.

How to appeal it
CO-204Low

This service/equipment/drug is not covered under the patient's current benefit plan

The member's specific plan design does not include this service. It differs from a general non-covered denial in that it points at the current plan's benefit package rather than a blanket exclusion.

How to appeal it
CO-226High

Information requested from the billing/rendering provider was not provided or was insufficient/incomplete

The payer asked your office for information, most often records or a questionnaire, and either received nothing or judged the response incomplete, then denied the claim.

How to appeal it
CO-234Medium

This procedure is not paid separately

The payer treats this procedure as part of another service and never pays it on its own line. The accompanying remark code indicates the payer's reasoning.

How to appeal it
CO-252High

An attachment/other documentation is required to adjudicate this claim/service

The payer will not decide the claim until it receives supporting documentation such as radiographs, charting, or a narrative. It is not a judgment on the merits, just a demand for evidence.

How to appeal it
CO-B7Medium

This provider was not certified/eligible to be paid for this procedure/service on this date of service

The payer's records show the rendering provider was not credentialed, enrolled, or otherwise eligible for payment on the date of service. This is common with new associates whose credentialing lagged their start date.

How to appeal it
PR-1Patient responsibility

Deductible amount

The amount applied to the member's deductible, assigned to patient responsibility. It is not a denial and is not recoverable from the payer; the work is accurate posting and clean patient collection.

How to appeal it