Claim denial codes (CARC), explained

You billed the wrong payer or contractor — the claim needs to go to whoever is actually responsible for this patient/service.

Something required is missing or wrong on the claim itself — this is a paperwork/data error, not a clinical decision.

The service required prior authorization (or notification) that wasn't obtained before it was provided, so the payer denied it.

The payer believes another insurance is primary and should be billed before them.

The payer is holding the claim until you send supporting documentation — an operative note, records, an invoice, or a certificate. It's a documentation hold, not a clinical denial, and it always travels with at least one remark code naming what's needed.

The claim was submitted after the payer's filing deadline, so it was denied for timeliness.

The procedure was billed with a modifier that doesn't belong on it, or it needed a modifier that wasn't there.

Your billed charge was higher than the payer's allowed/contracted amount — the difference is a contractual write-off, not a real denial.

The service isn't covered, and under the CO group code the provider — not the patient — absorbs the charge (often because no valid advance notice was given).

This service depends on a related or qualifying claim — a primary procedure, a prior service, or the original claim it adjusts — that wasn't referenced here, so the payer can't connect them.

The ICD-10 diagnosis on the claim isn't valid for the date of service — typically because the code wasn't effective yet, was deleted or replaced in the annual update, or needs greater specificity for that date.

The payer reviewed the documentation and decided it doesn't support the level of service billed, so it downcoded or reduced payment. This is a documentation-vs-coding judgment, most often on E/M levels.

The payer thinks you billed too many units, or the service too often, for what the documentation supports.

The payer won't pay this service when it's performed or billed by this provider type — the service is outside what that provider type/specialty is recognized to perform or bill under the plan.

The referring provider listed on the claim isn't eligible to refer this service — usually an enrollment, NPI, or provider-type issue — so the payer denied the referred service.

An authorization existed, but the service went beyond what it covered — more units, visits, or a longer span than the authorization approved — so the excess was denied.

The item or service isn't covered under the patient's current benefit plan as billed. Under the CO group code the provider — not the patient — absorbs it, unless valid advance notice (or a covered alternative) changes the picture.

The adjustment is the result of a review organization's (or the payer's) determination — a utilization, peer, or audit review concluded the service shouldn't be paid as billed. The decision rests on that review's findings.

The provider billed more hours, days, or units in the period than the contract allows. The limit is at the PROVIDER level (not per patient), so the excess over the contracted maximum was denied.

The payer asked the provider for additional information — records, an itemization, or documentation — and it wasn't supplied, came in late, or was incomplete, so the claim was adjusted.

This line reflects what a prior payer already paid or adjusted, factored into how this payer calculated its share — a coordination-of-benefits accounting entry, not a denial of the service itself.

Two procedures billed for the same day/setting are mutually exclusive — by coding rules they shouldn't both be performed/reported together — so the payer paid one and denied the other as billed.

The payer considers this procedure packaged into the payment for another service — it isn't separately payable, so it was bundled rather than paid on its own line.

An NCCI conflict: the two procedure (or procedure/modifier) combinations billed for the same day aren't compatible under the National Correct Coding Initiative — or a workers'-comp state rule — so one isn't separately payable as billed.

The payer says this service is already covered under a capitation or managed-care arrangement — the practice is paid a fixed per-member amount for these services, so the individual claim isn't separately reimbursed.

The plan says the services weren't provided by an in-network (or the required primary-care) provider. Under the CO group code the difference is treated as a provider/contractual responsibility rather than a patient balance.

Your managed-care contract with this payer doesn't make this service payable — it's carved out, excluded, or outside the contract's terms, so it was denied under the contractual group code.

The service didn't meet the payer's specific coverage or program guidelines — a policy-based denial where a required condition, criterion, or program rule wasn't satisfied as billed.

The service went over the payer's coverage limit — a frequency cap, visit limit, dollar maximum, or benefit allowance was exceeded, so the amount beyond the limit was denied.

An authorization number is on the claim and may be valid, but it doesn't match the services billed — the auth was for different codes, units, dates, or a different site than what was performed.

The service required a referral that wasn't on file, so the payer denied it. It's the referral counterpart to a missing authorization — the gatekeeping step the plan requires wasn't completed or recorded.

The medical plan received the claim but these are vision-benefit services, so they belong to the patient's separate vision plan. The fix is to refile to the vision plan, not to appeal the medical plan.

The billing provider's enrollment, contract, or credentialing doesn't allow payment for this specific service — a provider-eligibility problem, not a clinical one.

The payer can't match the patient to an active member on its file as billed — the member ID, name, or date of birth doesn't tie to a covered person, or the claim went to the wrong plan entirely.

The payer decided the service wasn't medically necessary for the diagnosis submitted, so it won't pay — and under CO the provider absorbs it unless a prior notice shifted liability.

The payer considers this service, procedure, or drug experimental or investigational under its medical policy — not yet accepted as standard care — so it won't pay. Under the CO group code the provider, not the patient, absorbs it unless valid advance notice shifted liability.

The payer applied a multiple-procedure payment reduction: when several procedures are performed together, the highest-valued one is paid in full and the others are reduced under standard multiple/concurrent-procedure rules.

The payer says a required plan process wasn't followed — a referral, prior authorization, network rule, or notification step was skipped — so the service was denied even though it might otherwise be covered.

This is a bundling denial — the payer says the service is already paid for as part of another code you billed, so it won't pay separately.

The diagnosis on the claim doesn't clinically support the procedure you billed, so the payer rejected the pairing.

The diagnosis code itself isn't on the payer's covered list for this service — the issue is the diagnosis, not the procedure's necessity.

The payer sees this as an exact duplicate of a claim/line it already received for the same patient, date, and service.

The item or drug isn't covered under the patient's current benefit plan as billed, and under the PR group code the patient is responsible.

The service isn't covered under the patient's plan, and under the PR group code the patient is responsible for the charge.

The same lacks-information problem as CO-16, reported under the patient-responsibility group — often because information the PATIENT needed to supply (coordination of benefits, accident details, a form) is missing. The paired remark names exactly what's needed.

The patient didn't meet the plan's eligibility requirements for this service — a waiting period, enrollment condition, or qualification wasn't satisfied — so the plan won't pay and the balance is the patient's.

The service fell during a gap in the patient's coverage — a period when no plan was active — so the plan won't pay and the balance is the patient's. Confirm the lapse dates before billing.

The payer asked the patient (or insured/responsible party) for information — coordination of benefits, accident details, a questionnaire — and it wasn't provided or was incomplete. Until the patient responds, the balance can fall to them.

The services weren't provided by an in-network (or the required primary-care) provider, and under the PR group code the balance is the patient's — typically because the patient chose to go out-of-network or bypassed required coordination.

The services weren't authorized by the network or primary-care provider the plan requires. Reported under the patient-responsibility group, but the first move is to check whether the required authorization/referral can still be obtained before billing the patient.

The service was provided after the patient's coverage ended, so the plan won't pay and the balance is the patient's. The key is confirming the actual termination date before billing the patient.

The service didn't meet the payer's coverage or program guidelines, reported under the patient-responsibility group. Verify whether the guideline was genuinely unmet — and whether the patient was properly notified — before treating the balance as theirs.

A secondary payer isn't covering the patient-responsibility amounts (deductible, coinsurance, copay) left by the primary payer, so those amounts remain the patient's to pay. It's common when the secondary plan doesn't pick up the primary's cost-share.

The services were provided outside the plan's preferred (narrow) network, and under the PR group code the resulting balance is the patient's — typically because the patient chose a provider outside the member's preferred network.

A required referral wasn't on file, reported under the patient-responsibility group — often because the patient went to a specialist without the plan's required referral. Check whether a referral can still be obtained before treating the balance as the patient's.

This amount is the patient's copay for the visit or service — a fixed cost-share defined by their plan. The claim adjudicated correctly; the copay is collectible from the patient, ideally at the time of service.

The payer can't match the patient to an active member on its file. Reported under the PR group, but the first move is to verify the patient's coverage — the usual cause is a fixable data error or a wrong payer, not a true patient balance.

The billed charge exceeded the allowed amount, and under the PR group code the excess is the patient's responsibility — which generally happens only with non-participating providers where balance billing is permitted.

The payer considers the service experimental or investigational, and under the PR group code the patient is responsible — typically because the patient was notified in advance and accepted the cost. Confirm valid advance notice before billing them.

This amount is the patient's responsibility because it applies to their unmet annual deductible — the claim processed correctly.

This line reflects what the primary payer already paid or adjusted, so the secondary payer can calculate its share — it's an accounting adjustment, not a denial.

The payer sees this as an exact duplicate of a claim/line it already received for the same patient, date, and service. Under the OA group code it's an informational duplicate adjustment, not a patient balance.

The same data/paperwork problem as CO-16, but flagged under the Payer Initiated group: something required is missing or invalid on the claim and must be fixed before the payer can process it. It is a data error, not a clinical decision, and the patient is not liable.

Like CO-252 but under the Payer Initiated group: the payer needs supporting documentation before it can adjudicate the claim. It's a documentation hold the provider resolves by supplying what the paired remark asks for — the patient is not liable.

A bundling adjustment — like CO-97 but under the Payer Initiated group: the payer says this service is already paid for as part of another code that was adjudicated, so it isn't paid separately. Under the PI group code the patient is not liable.