Denial Code Resolution Database

The amount was applied to the patient’s deductible. The payer adjudicated the claim correctly and paid nothing because the patient has not yet met their annual deductible.

Likely cause

Normal plan design, not an error. It becomes a revenue problem only when the practice never verified the remaining deductible at check-in and so collected nothing at the time of service.

Documentation to pull

The remittance advice showing the deductible application, and the eligibility response captured before the visit.

Resolution / appeal angle

Not appealable — nothing was denied. Bill the patient. If deductible amounts are routinely a surprise, the fix is upstream: real-time eligibility with deductible-remaining capture at scheduling.

The amount is the patient’s coinsurance — their percentage share of the allowed amount after the deductible is satisfied.

Likely cause

Plan design. Recurs as bad debt when coinsurance is not estimated and collected at or near the time of service.

Documentation to pull

Remittance advice and the plan’s coinsurance percentage from the eligibility response.

Resolution / appeal angle

Not appealable. Bill the patient. Where coinsurance is predictable — surgical, imaging, infusion — estimate and collect before the service.

The amount is the patient’s fixed copay for the visit.

Likely cause

Plan design. A copay appearing on the remit rather than in your collections means it was not taken at the front desk.

Documentation to pull

Remittance advice and the eligibility response showing the copay tier.

Resolution / appeal angle

Not appealable. This is the single cheapest dollar in the revenue cycle to collect and the most expensive to chase later — collect it at check-in.

The modifier you appended does not agree with the procedure code it was attached to — either the modifier is not permitted on that code, or a modifier the payer requires is missing.

Likely cause

Most often a missing laterality (RT/LT), a missing 25 on a same-day E/M, a 59/X{EPSU} applied where the payer expects a different distinct-service modifier, or a modifier carried over from a template.

Documentation to pull

The operative or procedure note supporting the modifier, the payer’s modifier policy for that code, and the NCCI edit pair if two procedures were billed together.

Resolution / appeal angle

Usually corrected and resubmitted rather than appealed — this is a claim defect, not a coverage decision. Appeal only when the documentation genuinely supports the modifier and the payer applied its own policy incorrectly; attach the note and cite the policy section.

Specialty note

Orthopaedics and podiatry generate this constantly through laterality; dermatology through multiple-lesion modifiers; physical therapy through the therapy modifiers.

The diagnosis submitted does not support the procedure billed, in the payer’s view.

Likely cause

A diagnosis truncated to an unspecified code, the diagnosis pointer aimed at the wrong line, or a screening-versus-diagnostic mismatch where the encounter changed character mid-visit.

Documentation to pull

The full encounter note, the complete diagnosis list with pointers, and the payer’s LCD/NCD or medical policy listing covered diagnoses for that procedure.

Resolution / appeal angle

Check the pointer first — a large share of these are a pointer error, not a clinical one, and resubmit correctly. Where the diagnosis is right, appeal with the note and the covered-diagnosis policy, quoting the specific ICD-10 code from the payer’s own list.

Specialty note

Gastroenterology sees this when a screening colonoscopy converts to diagnostic after a polyp is found and the diagnosis order is not updated.

Heads up: DEACTIVATED 1 May 2018 — replaced in practice by CARC 197. Competitor "top denial codes" listicles routinely still list this as live. Treating it as current is a visible accuracy error.

A retired authorization-related code. It stopped being valid on 1 May 2018 and must not appear on current remittance advice.

Likely cause

If you are seeing this on a 2026 remit, you are almost certainly reading an old denial report, a stale internal mapping table, or a vendor’s outdated code list.

Documentation to pull

Check the date of the remittance you are working. Then check your clearinghouse or PM system’s denial-mapping table for retired codes.

Resolution / appeal angle

Nothing to appeal. For current prior-authorization denials, work CARC 197 instead.

Heads up: Never work this code alone. X12 requires at least one paired remark code — that remark code, not the CARC, tells you what to fix.

The claim is missing information the payer needs, or contains a submission error. On its own it tells you almost nothing — the paired remark code is where the actual reason lives.

Likely cause

Anything from a missing NPI or taxonomy to an absent referring provider, invalid subscriber ID, or missing accident date. The breadth is the point: it is a container, not a diagnosis.

Documentation to pull

Read the RARC that accompanies it — X12 requires at least one remark code with this CARC. That remark code is the real instruction.

Resolution / appeal angle

Correct and resubmit. Appealing a CARC 16 without first reading its remark code wastes the appeal. If your denial reports show CARC 16 without the paired RARC, your report is dropping data your 835 already contains.

Heads up: X12 specifies group code OA for this code, not CO — except where state workers’ compensation regulations require CO. A remit showing "CO-18" is using the code contrary to its stated usage rule.

The payer has already received an identical claim or service line and is rejecting this one as a duplicate.

Likely cause

Genuine resubmission without a corrected-claim frequency code, an automated rebill triggered before the original adjudicated, or two legitimately separate same-day services billed without a distinguishing modifier.

Documentation to pull

The original claim’s status and payment, the submission history from your clearinghouse, and the notes for both encounters if the services were genuinely distinct.

Resolution / appeal angle

If truly duplicate, no action. If the services were genuinely separate — two visits the same day, bilateral procedures, repeat labs — resubmit with the appropriate distinct-service or laterality modifier and the documentation showing they were separate encounters.

Another insurer is primary for this patient and must adjudicate before this payer will.

Likely cause

Coordination-of-benefits information is stale or absent — commonly a patient who gained secondary coverage, a Medicare beneficiary still working, or a child covered by both parents where birthday-rule order was assumed rather than verified.

Documentation to pull

The primary payer’s explanation of benefits, the patient’s current COB information, and the eligibility response showing coverage order.

Resolution / appeal angle

Not an appeal — a sequencing problem. Bill the primary, then submit to this payer as secondary with the primary’s EOB attached. If the payer’s COB record is simply wrong, have the patient update it with the insurer; a provider appeal will not change the payer’s COB file.

Heads up: X12 specifies group code OA only for this code.

This line reflects what a prior payer already did — their payment and adjustments — rather than a new decision by this payer.

Likely cause

Normal secondary-payer processing. It appears on the secondary remit to account for the primary’s adjudication.

Documentation to pull

The primary payer’s remittance, to confirm the amounts carried forward are correct.

Resolution / appeal angle

Not a denial. Verify the primary’s figures were transmitted accurately; where the secondary has mis-stated the primary’s allowed or paid amount, that is a correction request, not an appeal.

The service falls under a capitation arrangement or a managed care plan, so it is not separately payable fee-for-service.

Likely cause

The patient is enrolled in a capitated product — frequently a Medicare Advantage or Medicaid managed care plan — and the claim went to the wrong entity, or the practice is capitated for this member and billed fee-for-service anyway.

Documentation to pull

The patient’s plan enrolment, your capitation roster for the month of service, and the delegated entity responsible for payment.

Resolution / appeal angle

Rarely appealable. Confirm whether the member was on your cap roster. If they were not, resubmit to the correct payer or delegated group. If your roster and the payer’s disagree, that is a contracting conversation, not a claim appeal.

The patient’s coverage had already ended on the date of service.

Likely cause

Eligibility was verified too early, or not at all — coverage lapsed between scheduling and the visit. This is the classic front-end failure and it is entirely preventable.

Documentation to pull

The eligibility response with its transaction date and time, the termination date from the payer, and any coverage the patient has since obtained.

Resolution / appeal angle

Not usually appealable against the payer — they are correct that coverage ended. The recovery path is to identify the coverage that was active on that date and bill it, or to bill the patient. The real fix is eligibility verification on the day of service, not at scheduling.

The claim arrived after the payer’s filing deadline had passed.

Likely cause

A claim that sat in a work queue, a rejection that was never reworked, or a secondary claim that waited on a primary EOB past the secondary’s clock. Timely filing denials are almost always an internal workflow failure rather than a payer error.

Documentation to pull

Proof of timely submission — the clearinghouse acceptance report with its date stamp is the single most useful artefact. Also the payer’s published filing limit and, critically, your contract, which usually overrides the published limit.

Resolution / appeal angle

Appeal only with proof of original timely submission, or a qualifying exception. For Medicare fee-for-service the deadline is federal and uniform — one calendar year from the date of service under 42 CFR 424.44 — and CMS lists only four narrow exceptions. Note that a Medicare timely-filing denial is not an initial determination and carries no appeal rights.

The payer cannot match the patient to a member record at all.

Likely cause

A transposed member ID, a name that does not match the card, a wrong date of birth, or the patient presenting a card for a plan they have left. Frequently the patient simply handed over the wrong card.

Documentation to pull

A copy of the insurance card from the date of service, the patient’s demographics as submitted, and a fresh eligibility check.

Resolution / appeal angle

Correct and resubmit rather than appeal. Re-verify identity against the card, correct the member ID or demographics, and resubmit within the filing window — these often become timely-filing denials because they sit unworked.

Heads up: This is a contractual write-off, not a denial. Any "top denial codes" ranking that puts CO-45 first is counting contractual adjustments as denials, which inflates a denial rate by an order of magnitude. Exclude it from denial-rate numerators.

Your charge exceeded the contracted or fee-schedule allowed amount, and the difference has been written off.

Likely cause

Normal contractual adjustment. Your charge master is set above the contracted rate, which is expected and appropriate.

Documentation to pull

Your fee schedule for the payer, to confirm the allowed amount actually matches the contracted rate.

Resolution / appeal angle

Not a denial and not appealable as one. The genuine use of this code is contract auditing: if the allowed amount does not match your contracted rate, you have an underpayment to pursue — which is a contract dispute, not a claim appeal.

The service was treated as a routine or preventive exam, or a screening done alongside one, and is not covered under the terms applied.

Likely cause

A preventive visit billed without the preventive modifier, or a problem-oriented service bundled into a wellness visit because the two were not distinguished.

Documentation to pull

The encounter note showing whether a separate problem was addressed, and the payer’s preventive-services policy.

Resolution / appeal angle

Where a distinct problem was genuinely evaluated alongside the preventive service, resubmit with the appropriate distinct-service modifier and the note showing separate work. Where the visit really was purely preventive and the plan excludes it, the balance is the patient’s.

Specialty note

Primary care and gastroenterology see this most — particularly around screening services that convert to diagnostic during the encounter.

The payer has decided the service was not medically necessary as billed.

Likely cause

Documentation that does not connect the clinical rationale to the service, a diagnosis outside the payer’s covered list, or a frequency the policy does not support.

Documentation to pull

The complete clinical note, prior conservative treatment attempted and failed, relevant imaging or test results, and the payer’s LCD/NCD or medical policy — quoted by section.

Resolution / appeal angle

This is the code most worth appealing, because it is a coverage judgement rather than a claim defect. Build the appeal around the payer’s own policy criteria, addressing each criterion explicitly with the note text that satisfies it. A generic "service was medically necessary" letter fails; a criterion-by-criterion mapping succeeds far more often.

Payment was reduced under multiple-procedure or concurrent-service rules — for example multiple surgeries in one session, multiple imaging studies, or concurrent anaesthesia.

Likely cause

Expected reimbursement methodology rather than an error. The reduction is applied to the lower-valued procedures in a session.

Documentation to pull

The operative note showing the procedures performed and the payer’s multiple-procedure reduction policy.

Resolution / appeal angle

Verify the reduction was applied in the correct order — payers occasionally reduce the higher-valued procedure. Where procedures were genuinely distinct sessions rather than one, resubmit with documentation of the separate sessions.

Specialty note

Orthopaedics, radiology and anaesthesia encounter this routinely; it is a reimbursement rule, not a denial to fight.

A required plan procedure was not followed — commonly a missing referral, an out-of-network service without authorization, or care delivered outside the plan’s rules.

Likely cause

Referral or authorization requirements that differ by product line within the same payer, or a patient who self-referred to a specialist under a plan requiring gatekeeping.

Documentation to pull

The referral or authorization on file, the plan’s specific procedural requirement, and evidence of any attempt made to obtain it before the service.

Resolution / appeal angle

Appeal where a referral existed but was not attached, or where the requirement was satisfied and mis-recorded. Retroactive referral is sometimes obtainable from the referring physician; many plans allow a short retro window.

Heads up: The group code changes the entire downstream action. CO-96 and PR-96 are the same reason with opposite financial outcomes.

The service is not covered. Whether the patient can be billed depends entirely on the group code: PR means billable to the patient, CO means written off.

Likely cause

A plan exclusion, a statutorily excluded service, or a service outside the benefit. Also appears where a service needed an advance beneficiary notice that was not obtained.

Documentation to pull

The plan’s exclusion language, the paired remark code, and any signed advance notice of non-coverage.

Resolution / appeal angle

Read the group code before doing anything — it determines whether you have a patient balance or a write-off. X12 requires at least one paired remark code with this CARC; that remark is where the specific exclusion is identified. Appeal only if the exclusion is being misapplied to a covered service.

The service is bundled — its payment is already included in another service that was adjudicated, so it is not separately payable.

Likely cause

NCCI bundling edits, a global surgical package, or a component service billed alongside the comprehensive code.

Documentation to pull

The NCCI edit pair and its modifier indicator, the operative note, and the global period rules for the primary procedure.

Resolution / appeal angle

Check the NCCI modifier indicator first: indicator 1 means a modifier may unbundle the pair where documentation supports a genuinely distinct service; indicator 0 means it cannot be unbundled at all and appealing is futile. Where the service was genuinely separate, resubmit with the appropriate distinct-service modifier and the note.

This payer is not responsible for the claim and is telling you to send it elsewhere.

Likely cause

The patient has moved to a Medicare Advantage plan while the claim went to traditional Medicare, the wrong MAC jurisdiction was billed, or the member changed carriers.

Documentation to pull

A current eligibility response identifying the correct payer, and the patient’s current card.

Resolution / appeal angle

Not appealable — rebill the correct payer promptly. These become timely-filing denials at the correct payer when they sit, so work them the same week they arrive.

The patient has used up a benefit maximum — a visit cap, a dollar limit, or an annual allowance for this service.

Likely cause

Plans with hard caps on therapy visits, behavioral health sessions, chiropractic visits or DME allowances, where utilization was not tracked.

Documentation to pull

The accumulated utilization from the eligibility response, the plan’s benefit limit, and clinical justification for continued care.

Resolution / appeal angle

Where the cap is genuinely exhausted the balance is usually the patient’s and appeal will fail. Where medical necessity supports an exception, some plans have a documented exception process — use that route rather than a standard appeal. Track remaining visits at each encounter to prevent recurrence.

Specialty note

Physical therapy, behavioral health and chiropractic are the highest-exposure specialties; visit-count tracking should be a standing part of their intake.

Information from prior processing of this claim appears incorrect, so the payer will not process the current submission as sent.

Likely cause

A corrected claim submitted without the right frequency code or original claim reference, or an adjustment that conflicts with what the payer has on file.

Documentation to pull

The original claim number, the original remittance, and the corrected claim as submitted with its frequency code.

Resolution / appeal angle

Resubmit as a properly identified corrected claim referencing the original claim number, rather than as a new claim. Submitting a correction as a fresh claim commonly produces this and then a duplicate denial.

The payer considers the documentation insufficient to justify this many services, or this frequency of service.

Likely cause

Units billed beyond the payer’s frequency limit, or time-based services whose documented time does not support the units.

Documentation to pull

Time documentation for timed services, the treatment plan showing frequency, and the payer’s frequency policy or medically-unlikely-edit threshold.

Resolution / appeal angle

Appeal with time-in/time-out documentation for timed codes and a treatment plan justifying frequency. This is winnable where documentation genuinely supports the units — but verify your unit calculation first, because miscounted time-based units are a common self-inflicted cause.

Specialty note

Physical, occupational and behavioral therapy see this most, because their codes are time-based and unit calculation errors are easy to make.

The diagnosis submitted is not covered under this plan for this service.

Likely cause

A diagnosis outside the payer’s covered list for the procedure, or an unspecified code used where the policy requires specificity.

Documentation to pull

The payer’s covered-diagnosis list for the procedure, and the clinical note supporting a more specific diagnosis if one applies.

Resolution / appeal angle

Compare the submitted diagnoses against the payer’s covered list. Where the record supports a covered diagnosis that was not submitted, correct and resubmit. Where the diagnosis is right and the policy is being misapplied, appeal quoting the policy.

Required prior authorization, precertification or notification was not obtained before the service.

Likely cause

Authorization never requested, obtained but not linked to the claim, expired before the date of service, or issued for a different code than the one performed.

Documentation to pull

The authorization number, its effective date range, the codes it covers, and any record of the request if it was made and not answered.

Resolution / appeal angle

Two distinct paths. If authorization existed but was not on the claim, resubmit with the number — this is a clerical fix, not an appeal. If it was never obtained, request retroactive authorization where the payer permits it, and otherwise appeal on medical necessity with the clinical record. Urgent and emergent services frequently have an exception, so check the policy before conceding.

Specialty note

This is the live prior-authorization code — CARC 15 was retired on 1 May 2018 and 197 was modified on the same date.

The patient’s plan simply does not include this item or service in its benefits — it is excluded by plan design rather than judged clinically unnecessary.

Likely cause

A benefit exclusion rather than a medical-necessity decision — the plan does not cover this category of item or service for this member at all.

Documentation to pull

The plan’s benefit exclusion language and any signed advance notice of non-coverage.

Resolution / appeal angle

A true exclusion is rarely overturned on appeal. The productive move is an advance notice of non-coverage before the service so the balance is cleanly billable to the patient. Verify the group code to determine whether you may bill them.

The payer asked the patient or subscriber for information and did not receive it, or received too little to adjudicate.

Likely cause

A coordination-of-benefits questionnaire, accident details, or a student or dependent status confirmation the patient never returned. The delay sits with the member, not the practice.

Documentation to pull

The payer’s request letter if the patient has it, and the patient’s current COB or accident information.

Resolution / appeal angle

A provider appeal will not resolve this — the payer needs the member to respond. Contact the patient, explain precisely what the insurer needs, and have them supply it directly. Then request reprocessing. Track these separately from clinical denials, because the intervention is patient outreach rather than claim work.

The procedure, or the procedure-and-modifier combination, conflicts with another one billed the same day under National Correct Coding Initiative rules or a workers’ compensation fee schedule.

Likely cause

An NCCI procedure-to-procedure edit pair billed together without a permitted modifier, or mutually exclusive procedures reported for the same session.

Documentation to pull

The NCCI edit pair with its modifier indicator, and the operative note establishing whether the services were genuinely separate.

Resolution / appeal angle

Look up the edit pair’s modifier indicator before responding. Indicator 0 means the pair can never be unbundled and there is nothing to win. Indicator 1 means a distinct-service modifier may be applied where documentation genuinely supports separate anatomic sites, sessions or encounters — resubmit with the modifier and the note, do not simply append 59 and hope.

A general claim or service denial that carries no reason on its own — the paired remark code holds the actual explanation.

Likely cause

Used by payers as a catch-all when no more specific reason code applies.

Documentation to pull

The accompanying remark code, which is required and is the only place the real reason appears.

Resolution / appeal angle

Do not work this code without its remark code. Like CARC 16, it is a container. If your denial reporting shows A1 with no remark, the report is discarding information present in the 835.

The provider was not certified or eligible to be paid for this service on this date — a credentialing or enrolment problem rather than a coding one.

Likely cause

Enrolment not yet effective, a lapsed revalidation, a provider not credentialed with that specific plan or product, or a service outside the provider’s approved scope.

Documentation to pull

The provider’s enrolment effective date with that payer, revalidation status, and the specific plan or product the patient carries.

Resolution / appeal angle

Claim-level appeal rarely works because the underlying enrolment record is the problem. Fix the enrolment, then request reprocessing of held claims — many payers will retro-adjudicate to the enrolment effective date. Hold claims for new providers rather than submitting into a denial, and track revalidation dates as a standing calendar item.

Specialty note

The highest-cost denial category for new hires and new locations, because it silently accumulates across every claim a provider submits until enrolment is corrected.

Directs you to the plan’s benefit documents for restrictions applying to this service.

Likely cause

Accompanies a coverage-restriction denial where the specific limitation lives in plan documents rather than in the remit.

Documentation to pull

The plan’s summary of benefits and any medical policy for the service.

Resolution / appeal angle

Obtain the specific restriction language before appealing — the remark is a pointer, not a reason. Appeal only once you can name the restriction and show it does not apply.

The item or service does not meet the criteria for the benefit category it was billed under.

Likely cause

A service billed under a category whose criteria it does not satisfy — common with DME and with services that have specific coverage criteria.

Documentation to pull

The payer’s coverage criteria for the category, and clinical documentation addressing each criterion.

Resolution / appeal angle

Map the record against each published criterion. Where the service genuinely belongs in a different category, rebill correctly rather than appeal.

The referring provider’s identifier is missing, incomplete or invalid.

Likely cause

A missing or wrong referring NPI, or a referring provider not enrolled or not eligible to refer for this payer.

Documentation to pull

The referring provider’s NPI and their enrolment status with the payer.

Resolution / appeal angle

Correct and resubmit. Validate referring NPIs against the payer’s registry at order entry, since the same referring provider will otherwise generate this repeatedly across many claims.

Specialty note

Radiology, laboratory and DME carry the highest exposure, because every claim depends on a referring provider identifier supplied by someone outside the practice.

The rendering provider’s identifier is missing, incomplete or invalid.

Likely cause

A missing rendering NPI, a mismatch between the rendering provider and the group’s enrolment, or a locum or supervising arrangement billed without the correct identifiers and modifiers.

Documentation to pull

The rendering provider’s NPI, their enrolment with the payer, and any supervision or locum arrangement documentation.

Resolution / appeal angle

Correct and resubmit. Recurring instances usually indicate a provider record configured incorrectly in the practice management system rather than a per-claim error.

The number of days or units billed exceeds what the payer will accept for this service.

Likely cause

Units exceeding a medically-unlikely-edit threshold, or a unit calculation error on a time-based code.

Documentation to pull

Time documentation for timed services, and the payer’s unit limit or MUE value for the code.

Resolution / appeal angle

Recalculate the units first — unit errors on time-based codes are the most common cause and are not appealable. Where the units are genuinely correct and clinically supported, appeal with time documentation and the treatment rationale.

Instructs you to submit a new claim containing the information that was requested.

Likely cause

Accompanies an unprocessable claim where the payer wants a fresh submission rather than a correction or appeal.

Documentation to pull

Whatever the paired reason code identified as missing.

Resolution / appeal angle

Do exactly what it says — submit a new claim, not an appeal and not a corrected claim. Watch the filing clock, which usually continues running.

Secondary payment cannot be considered because the primary payer’s identity or payment information was missing or unreadable.

Likely cause

A secondary claim submitted without primary payment details, or with an illegible or improperly formatted primary EOB.

Documentation to pull

The primary payer’s remittance with paid amounts, adjustments and adjudication date.

Resolution / appeal angle

Resubmit the secondary claim with complete, legible primary payment information — ideally electronically rather than as a scanned attachment. Watch the secondary payer’s filing clock, which is frequently shorter than the primary’s and is measured from the primary’s adjudication date.

Heads up: No appeal rights attach to an unprocessable claim. Correct and resubmit; an appeal will not be adjudicated.

The claim was incomplete or invalid, so it was never processed — and because it was never processed, no appeal rights attach to it.

Likely cause

Missing or invalid data that stopped the claim before adjudication.

Documentation to pull

The claim as submitted, compared against the payer’s required-field list.

Resolution / appeal angle

Do not appeal — you cannot. Correct the claim and submit it anew. Appealing an unprocessable claim wastes the appeal window and produces no decision, and this is one of the most commonly mishandled remarks in denial work.

The service is not covered when performed in the same session or on the same date as another service already processed for that patient.

Likely cause

Same-session bundling — two services billed for one encounter where the payer pays only one.

Documentation to pull

The note establishing whether the services were genuinely separate sessions, and the payer’s same-day policy.

Resolution / appeal angle

Where the services were genuinely separate sessions, resubmit with a distinct-service modifier and documentation of the separate encounters, including times. Where they were one session, the bundling is correct.