Insurance denial and CARC code lookup
Decode CO, PR, and CARC codes on your EOB and see appeal next steps.
Use this free denial code lookup to search Claim Adjustment Reason Codes (CARC) such as CO-50, CO-16, and PR-204 on your EOB. Each result links to a plain-language guide and the appeal letter generator. Codes are plan-specific; always compare the code on your remittance to the payer’s written denial.
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Example: Search or — CARC and RARC results include appeal tips.
16 CARC guides indexed · 12 common RARC entries
carcCO-45 — Charge Exceeds Fee Schedule
The insurer reduced payment because the charge exceeds the contracted or fee schedule amount.
Appeal tip: Request the fee schedule, contract rate, and itemized allowed amount calculation.
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carcCO-50 — Non-Covered Services
The payer determined the service is not medically necessary or is otherwise non covered under the benefit plan.
Appeal tip: Cite plan documents, medical necessity, and applicable federal appeal rights.
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carcCO-96 — Non-Covered Charge
The procedure or supply is not covered under the patient's current benefits.
Appeal tip: Submit clinical records demonstrating medical necessity and prior authorization if applicable.
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carcCO-97 — Payment Included in Allowance
The benefit for this service is included in the payment or allowance for another procedure that was already adjudicated.
Appeal tip: Request bundling rationale and unbundle with operative reports and coding documentation.
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carcCO-151 — Frequency Limitation
The payer reduced payment because the documentation does not support this many services or this frequency of services.
Appeal tip: Submit clinical records showing medical necessity for each visit or unit, prior auth if required, and plan frequency rules.
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carcCO-16 — Missing Information
The claim or service lacks information or has submission or billing errors needed for adjudication.
Appeal tip: Provide all missing fields and request reprocessing within appeal deadlines.
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carcCO-167 — Diagnosis Not Covered
The diagnosis or diagnoses on the claim are not covered under the patient's benefit plan.
Appeal tip: Verify ICD coding against medical records and appeal with documentation of a covered diagnosis.
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carcCO-18 — Duplicate Claim
The payer considers this claim a duplicate of a previously processed claim.
Appeal tip: Clarify distinct dates of service or corrected claim submission with supporting documentation.
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carcCO-22 — Coordination of Benefits
Another payer may be responsible for this claim.
Appeal tip: Submit EOB from primary insurer and request coordination of benefits reconsideration.
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carcCO-29 — Timely Filing Limit
The claim was not filed within the payer's required timeframe.
Appeal tip: Document proof of original submission, portal errors, or good cause for late filing.
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carcPR-204 — Service Not Covered Under Benefit Plan
This service, equipment, or drug is not covered under the patient's current benefit plan and may be patient responsibility.
Appeal tip: Review plan exclusions in your SPD and appeal if coverage was misapplied or miscoded.
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carcCO-4 — Modifier Inconsistent
The procedure code modifier is inconsistent with the billed service.
Appeal tip: Correct modifier usage with operative notes and coding clarification letter.
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carcCO-197 — Prior Authorization Required
Prior authorization or precertification was not obtained.
Appeal tip: Argue retrospective authorization, emergency exception, or provide retro auth approval.
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carcCO-204 — Service Not Covered Under Benefit Plan
This service is excluded from the patient's benefit plan.
Appeal tip: Cite plan language, medical policy, and applicable appeal rights under ERISA or ACA.
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carcCO-11 — Diagnosis Inconsistent with Procedure
The diagnosis code on the claim is inconsistent with the procedure performed according to payer edits.
Appeal tip: Verify ICD-10 and CPT pairing with your provider, submit corrected coding with clinical notes, or appeal if the diagnosis supports the service.
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carcCO-27 — Expenses After Coverage Terminated
Expenses were incurred after the patient's coverage terminated.
Appeal tip: Verify eligibility on the date of service, COBRA or grace-period rights, and employer enrollment records.
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rarcN130 — Consult plan benefit documents
The payer asks you to consult plan documents for benefit limits or exclusions.
Appeal tip: Request the specific plan provision cited and compare to your SPD or EOC.
rarcN386 — Not covered when deemed not medically necessary
Service denied as not medically necessary under plan rules.
Appeal tip: Appeal with treating clinician notes; pair with CO-50 disputes on the same line.
rarcN522 — Duplicate claim/service
Payer treats the line as a duplicate of a prior paid or pending claim.
Appeal tip: Provide proof of distinct date of service, modifier, or corrected claim number.
rarcN657 — This should be billed by the facility
Professional component may be bundled or should be billed by the facility.
Appeal tip: Verify place of service and split billing rules; include operative report if applicable.
rarcN781 — Missing/incomplete/invalid prior authorization
Prior authorization was not on file or did not match service details.
Appeal tip: Submit retro-auth proof, emergency exception, or appeal medical necessity with auth number if obtained late.
rarcN290 — Missing/incomplete/invalid diagnosis
Diagnosis code missing, invalid for date of service, or not covered for the procedure.
Appeal tip: Correct claim with clinician-supported ICD-10 code and appeal if denial persists after correction.
rarcN362 — Number of days/units exceeds maximum
Benefit maximum or frequency limit applied.
Appeal tip: Document medical need beyond the cap and request exception or medical necessity override.
rarcN425 — Statute of limitations / timely filing
Claim received after payer timely filing limit.
Appeal tip: Prove prior submission, payer delay, or coordination of benefits timing with proof of mailing.
Complete guide
How to use Denial codes in your appeal workflow
How it works
- You enter denial facts from your EOB or denial letter — member ID, claim number, service, and the reason the payer gave.
- AppealFlow drafts structured appeal language you can edit in the browser. Optional checkboxes add ERISA full-and-fair-review language, No Surprises Act references, or expedited-review requests when they fit your facts.
- Export PDF or Word, keep a copy for your records, and file through the portal, fax, or mailing address on your notice before the deadline printed there.
How denial and remark codes fit together
Your Explanation of Benefits lists billed charges, allowed amounts, and reason codes. Claim Adjustment Reason Codes (CARC) often start with CO (contractual obligation) or PR (patient responsibility). A CO-50 medical necessity denial is different from PR-1 deductible — the appeal path depends on which code the payer applied. Always compare the code on the remittance to the written denial letter; they should tell the same story.
Step-by-step: from code to appeal letter
Step 1: Photograph or download the EOB page with the code. Step 2: Search this lookup and open the matching denial-code guide for plain-language meaning. Step 3: Gather records that answer that specific reason (clinical notes for CO-50, authorization numbers for CO-197, etc.). Step 4: Draft a letter with the general or specialty generator citing claim number, date of service, and the code. Step 5: File through the channel on your notice before the internal appeal deadline.
When a code is not really a denial
Some CO codes explain discounts while the plan still pays. PR codes may show your copay even when the claim is approved. If paid amount is greater than zero, you may still owe patient responsibility without needing a full medical necessity appeal — though billing errors should be disputed separately.
Worked example: estimating a 180-day internal window
Your commercial plan sends an adverse benefit determination dated March 15, 2026 denying physical therapy as not medically necessary. The notice says you may request an internal appeal within 180 days. Adding 180 calendar days to March 15 lands on September 11, 2026 (verify with your plan — some policies use business days or a fixed date on the form). If you need continued care while waiting, ask whether the plan offers an expedited review and document any worsening symptoms. If the internal appeal is upheld, the same notice often explains whether you may request external review and which state or federal program applies. Save portal uploads, fax confirmations, and certified mail receipts.
Appeal deadlines by plan type (reference)
Deadlines are plan-specific. The table summarizes common federal frameworks cited on many notices. Your adverse benefit determination letter controls filing dates and channels.
| Plan type | Internal appeal | External review | Urgent / expedited |
|---|---|---|---|
| ACA marketplace / fully insured individual & small group | Often 60–180 days from the adverse determination (check notice). ACA internal claims and appeals rules require written notice of rights. | After exhausting internal appeals, many enrollees may request external review; federal rules set minimum external review rights for qualifying plans (see 45 CFR 147.136). | Urgent medical situations may qualify for expedited review; many plans must respond within 72 hours when delay could seriously jeopardize health (45 CFR 147.136(b)(3) framework). |
| Self-funded employer plan (ERISA) | 29 CFR 2560.503-1 requires a reasonable opportunity for a full and fair review; many plans allow about 180 days to request review of an adverse benefit determination unless the plan document grants longer. | External review rights depend on plan design and state law for insured portions; many ERISA plans use independent review vendors after internal exhaustion. | Expedited review must be available when the timeframe for a standard review could seriously jeopardize life or health (29 CFR 2560.503-1(h)(3)(i)). |
| Original Medicare (Part A & B) | Medicare uses redetermination (Level 1) by the Medicare Administrative Contractor — typically 120 days from the date of the initial determination on the MSN. | Reconsideration (Level 2), ALJ hearing, and further levels follow CMS Medicare appeals guidance — not the same clocks as commercial insurance. | Expedited Medicare determinations exist for certain hospital and SNF situations; follow instructions on the MSN. |
| Medicare Advantage (Part C) | Organization determination and plan-level appeals follow CMS Medicare Advantage rules; use the plan's forms and clocks on the denial. | After plan-level appeals, enrollees may request CMS review or, for some issues, state external review when applicable. | Part C plans must offer expedited reviews for urgent requests per CMS marketing/appeals requirements. |
| Medicare Part D (prescription drugs) | Coverage determinations and exceptions use PBM/plan Part D forms; standard determination timeframes are set in CMS Part D regulations. | Appeal to the Independent Review Entity (IRE) after plan-level denial of a standard or expedited determination. | Expedited exceptions and appeals exist when waiting could seriously harm health; request expedited processing in writing. |
| Medicaid / CHIP (state) | Each state Medicaid agency sets fair hearing and appeal timelines; use the notice from your managed care plan or state agency. | State fair hearing after managed care appeal exhaustion; timelines vary by state and benefit type. | Many states allow expedited hearings when delay would jeopardize health; cite urgency on the request form. |
Cite 29 CFR 2560.503-1 for many ERISA group health plans and 45 CFR 147.136 for many non-grandfathered individual/small group plans. Medicare and Medicaid use separate statutes and forms.
Common mistakes
- Treating an illustrative calculator result as a legal deadline without reading your notice.
- Filing with the medical claims address when the denial is a pharmacy benefit determination.
- Skipping the internal appeal and going straight to external review before the notice allows it.
What to do next
- Save proof of filing (portal screenshot, fax confirmation, or certified mail receipt).
- If the plan requests more records, respond within the timeframe on the follow-up letter.
- When internal appeals are exhausted, read your notice for external review or state complaint rights.
- Need deadlines, evidence lists, and filing checklists in one download? Consider the matching AppealFlow pack on the pricing page (document prep only).
- Matching paid document pack
- General appeal letter generator
- Denial code lookup