Insurance Denial & Appeal Terms Explained

This glossary exists because insurance denials come wrapped in jargon — CARC codes, adjustment groups, remittance advice — that slows down your response when speed matters. It is built for billing professionals, revenue cycle teams, practice managers, and patients who need to understand what a denial means and what to do next, without wading through payer policy manuals.

Denial Codes

The standardized codes on your EOB that tell you exactly why a line item was denied or adjusted.

• CARC CodeStandardized number on an EOB explaining why a claim or line item was adjusted or denied.
• RARC CodeSupplemental remark code providing additional detail alongside a CARC code.
• CARC 97Service bundled into another procedure already paid — the most common bundling denial.
• CARC 50Medical necessity denial — payer determined the service was not required.
• CARC 29Timely filing denial — claim submitted after the payer's deadline.
• CARC 197Prior authorization missing, incomplete, or not applicable to the billed service.
• CARC 4Modifier inconsistent with the procedure billed — modifier error denial.
• CARC 96Non-covered charge — service not a benefit under the patient's plan.
• CARC 18Exact duplicate claim — payer already processed an identical submission.
• CO DenialContractual obligation adjustment — provider cannot bill the patient for this amount.
• PR DenialPatient responsibility — deductible, copay, or coinsurance owed after adjudication.
• OA DenialOther adjustment — catch-all category outside CO and PR responsibility.

Appeal Process

The formal steps, deadlines, and review types used to overturn a denied or reduced claim payment.

• Insurance AppealFormal written request to a payer to reverse a denied or reduced claim payment.
• First-Level AppealInitial internal review request submitted directly to the payer after a denial.
• Second-Level AppealFollow-up appeal when first-level review is denied — reviewed by a different payer team.
• External AppealIndependent review outside the insurance company — required by law in most states.
• Independent Medical Review (IMR)Independent physician review of a medical necessity denial with no payer relationship.
• Appeal DeadlineTime limit to submit an appeal after a denial — typically 30 to 180 days by payer.
• Medical NecessityPayer determination that a service is appropriate and required for the patient's condition.
• Peer-to-Peer ReviewDirect conversation between treating physician and payer medical director before formal appeal.
• Remittance Advice (EOB)Payer document explaining how each claim was processed, paid, denied, and coded.
• Claim AdjustmentAny payer change to the billed amount — reductions, denials, or patient responsibility.
• Timely Filing LimitDeadline to submit a claim after date of service — missing it triggers CARC 29.
• Appeal Success RatePercentage of denied claims overturned after formal appeal — 40% to 75% by denial type.

Regulations and Law

Federal and state rules that govern coverage decisions, appeal rights, and payer obligations on denied claims.

• ERISAFederal law governing employer-sponsored health plans and establishing the right to appeal denied claims.
• ACA Appeal RightsAffordable Care Act protections requiring internal and external appeal processes for denied claims.
• NCCI (National Correct Coding Initiative)CMS edit system preventing improper payment of procedure code combinations billed together.
• NCCI Bundling EditSpecific NCCI rule prohibiting separate billing when one code is a component of another.
• LCD (Local Coverage Determination)Medicare contractor decision on whether a service is covered in a specific geographic area.
• NCD (National Coverage Determination)Nationwide Medicare policy determining coverage for all beneficiaries.
• EMTALAEmergency treatment law requiring hospitals to provide care regardless of ability to pay.
• State Prompt Pay LawState rules requiring insurers to pay clean claims within 30 to 45 days.
• Prior Authorization RequirementPayer rule requiring pre-approval of certain services before rendering or billing.
• Medical Necessity CriteriaClinical standards and guidelines payers use to determine whether a service is covered.
• Surprise Billing ProtectionNo Surprises Act limits on out-of-network patient billing beyond in-network cost-sharing.
• Coordination of Benefits (COB)Process determining primary payer when a patient has multiple insurance plans.

Billing and Coding

The codes, claim elements, and billing concepts that determine whether a claim pays cleanly or comes back denied.

• CPT CodeFive-digit procedure code identifying the medical service billed on a claim.
• ICD-10 CodeDiagnosis code justifying the medical necessity of the procedure billed.
• ModifierTwo-digit code appended to a CPT code describing how a service was performed.
• Clean ClaimClaim with all required information that can be processed without additional provider input.
• Claim ScrubbingPre-submission automated review catching errors that would cause denials.
• Fee ScheduleMaximum payer reimbursement amount for a specific procedure code.
• Allowed AmountMaximum insurer payment for a covered service — basis for contractual write-offs.
• EOB (Explanation of Benefits)Insurer document showing billed, allowed, paid, and patient-owed amounts.
• Place of Service CodeTwo-digit code indicating where a service was rendered — errors cause denials.
• Revenue CodeFour-digit institutional claim code identifying the type of service billed.
• Global PeriodPostoperative window where related services are included in the surgical fee.
• Incident-To BillingMedicare rule allowing staff services billed under the supervising physician's NPI.
• Claim Denial RatePercentage of submitted claims denied — industry average 5 to 10 percent.

Payers and Plans

Insurance plan types, payer structures, and coverage rules that shape how claims are processed and denied.

• Commercial InsurancePrivate employer or individual coverage governed by state law or ERISA.
• MedicareFederal program for people 65+ and certain disabled individuals — CMS rules and appeals.
• MedicaidJoint federal-state program for low-income individuals with state-specific coverage rules.
• Medicare Advantage (Part C)Private plans contracting with Medicare — own prior auth rules and denial patterns.
• TRICAREHealth coverage for military members, retirees, and families — DoD-administered.
• HMO (Health Maintenance Organization)Network-only plan requiring referrals — out-of-network denials without prior auth.
• PPO (Preferred Provider Organization)Flexible network plan paying reduced rates for out-of-network care.
• Self-Funded PlanEmployer pays claims directly — governed by ERISA, not state insurance law.
• Fully Insured PlanEmployer pays premiums to an insurer that assumes financial risk.
• Network StatusWhether a provider has a contracted rate with a specific health plan.
• Prior AuthorizationAdvance insurer approval required before certain services — top source of CARC 197.
• Payer PolicyInsurer coverage guidelines — primary document to cite in medical necessity appeals.
• Claims AdministratorEntity processing claims — often a TPA for self-funded employer plans.

Revenue Cycle

Financial metrics and operational processes from charge capture through final payment and denial recovery.

• Revenue Cycle Management (RCM)End-to-end claims process from registration through final payment.
• Days in ARAverage days to collect payment after service — denials drive elevated AR days.
• Denial ManagementSystematic tracking, appealing, and preventing claim denials.
• Write-OffUncollectable amount removed from AR — unappealed denials become permanent losses.
• Clean Claim RatePercentage of claims accepted on first submission — top performers above 95 percent.
• First-Pass Resolution RateClaims paid on first submission without resubmission or appeal.
• Accounts Receivable (AR)Money owed for services rendered but not yet collected.
• Charge CaptureRecording all billable services for submission — missed charges mean lost revenue.
• UnderpaymentInsurer pays below contracted rate — appealable revenue leakage separate from denials.
• OverpaymentInsurer pays above contracted rate — must be returned within 60 days under Medicare rules.
• CredentialingVerifying provider qualifications and payer enrollment — gaps cause denials.
• NPI NumberUnique 10-digit provider billing identifier — errors cause claim rejections.
• SuperbillProvider receipt with codes and charges for patient self-filing of claims.