CARC: Claim Adjustment Reason Code

What is a CARC?

A CARC (Claim Adjustment Reason Code) is one of the X12-standard codes US healthcare payers use on the 835 Electronic Remittance Advice (ERA) to explain every adjustment or denial on a claim line. Every line that gets paid less than the billed amount carries at least one CARC; high-denial practices see hundreds of distinct CARCs across their payer mix over a single month. CARCs are maintained by the X12N Insurance Subcommittee and published by the Washington Publishing Company (WPC).

CARC analytics is the highest-leverage revenue cycle workflow at most healthcare practices. The top 10 CARCs at any given organization typically account for 70–80% of denial dollars, and most of those are addressable through front-end workflow fixes rather than back-end appeals. A practice that systematically fixes its top 5 CARC categories typically lifts net collections by 1.5–3 percentage points within two quarters.

CARC, RARC, and CAS — what each one does

Three X12 elements appear together on every ERA adjustment and serve distinct purposes:

• CARC (Claim Adjustment Reason Code) — explains why the payer adjusted or denied the line. Three or four digit numeric code (e.g., 16, 97, 197).
• RARC (Remittance Advice Remark Code) — provides additional explanatory detail. Begins with N, M, or MA (e.g., N179, M86, MA01). A single line can carry one CARC and multiple RARCs.
• CAS (Claim Adjustment Segment) — the 835 segment that carries the Claim Adjustment Group Code plus the CARC plus the adjustment amount. Multiple CAS segments can appear on a single line for different adjustment categories.

Claim Adjustment Group Codes (CAGCs)

Every CARC is paired with a Claim Adjustment Group Code that classifies the adjustment by financial responsibility. There are five:

• CO (Contractual Obligation) — the adjustment is the provider's contractual responsibility under the payer agreement and cannot be billed to the patient. CO-97 (bundled), CO-45 (charge exceeds fee schedule), and CO-16 (missing information) are the most common.
• PR (Patient Responsibility) — the amount is the patient's financial responsibility. PR-1 (deductible), PR-2 (coinsurance), PR-3 (copayment) populate the patient statement.
• OA (Other Adjustment) — adjustments not classified elsewhere; less commonly used.
• PI (Payer-Initiated) — adjustments initiated by the payer that are neither contractual nor patient responsibility; specific to the payer's internal processing.
• CR (Correction or Reversal) — correction to a previously processed claim, typically reversing a prior payment when an adjustment is later identified.

The 20 highest-impact CARCs at most practices

Specific volume varies by specialty and payer mix, but the following CARCs typically dominate denial dollars across primary care, specialty, and hospital outpatient settings:

• CARC 197 — Precertification / authorization absent. Front-end workflow gap; appeals have a low success rate.
• CARC 16 — Claim/service lacks information. Documentation incomplete; payer rarely specifies the missing field.
• CARC 18 — Duplicate claim/service. Often a clearinghouse routing or resubmission workflow artifact, not a real duplicate.
• CARC 109 — Claim not covered by this payer. Eligibility verification gap; patient's coverage doesn't match what was billed.
• CARC 50 — Medical necessity not met. Service performed but documentation or payer policy doesn't support coverage.
• CARC 97 — Benefit included in another service. NCCI bundling violation.
• CARC 96 — Non-covered charge. Service excluded under the benefit plan.
• CARC 119 — Benefit maximum reached. Annual or lifetime cap on the service.
• CARC 29 — Time limit for filing has expired. Calendar-based denial; usually unappealable.
• CARC 22 — Care may be covered by another payer (COB). Coordination of benefits failure.
• CARC 23 — Impact of prior payer adjudication. COB sequencing problem.
• CARC 11 — Diagnosis inconsistent with procedure. ICD-10 to CPT mismatch.
• CARC 4 — Procedure modifier inconsistent or missing.
• CARC 24 — Charges covered under capitation or managed care agreement.
• CARC 27 — Expenses incurred after coverage terminated.
• CARC 31 — Patient cannot be identified as our insured. Demographic mismatch.
• CARC 151 — Information submitted does not support this many services (MUE-triggered).
• CARC 167 — Diagnosis not covered for this service.
• CARC 204 — Service not covered under patient's benefit plan.
• CARC 252 — Attachment or other documentation required to adjudicate.

How to look up CARC codes

Three reference sources are authoritative:

• Washington Publishing Company (WPC) — the X12N Insurance Subcommittee publishes the canonical CARC and RARC lists at wpc-edi.com. Updated three times per year, typically in March, July, and November. This is the definitive source for CARC text and effective dates.
• Your clearinghouse remit translator — Change Healthcare, Availity, Waystar, Trizetto, and other major clearinghouses ship CARC libraries embedded in their EOB display tools. Quality varies; some provide context-specific guidance, others only show the raw code text.
• Payer-specific CARC documentation — many payers publish guidance that maps internal denial categories to CARC codes. Aetna, Cigna, Humana, and Anthem all maintain published CARC-to-action mappings useful for routing remediation workflow.

CARC routing workflow

Mature denial management uses CARC to route each denied line to the correct workflow team within hours of ERA receipt — not the same shared queue:

• Front-end CARCs (197, 109, 31, 22, 23, 27) → registration, eligibility, and authorization team. Root cause is pre-service.
• Coding CARCs (97, 11, 4, 151) → coding team. Root cause is at code assignment or modifier application.
• Clinical-documentation CARCs (50, 167, 252) → clinical documentation team. Requires provider documentation review or supporting attachment to appeal.
• Operational CARCs (16, 18, 29) → billing operations. Root cause is in claim assembly or submission workflow.

Why CARC trend analytics drives recovery

Most denial dashboards report cumulative denial dollars by CARC year-to-date. That number is true but not actionable — it tells you nothing about whether a problem is growing. The view that drives intervention is week-over-week change in denied dollars by CARC, by payer. When CARC 197 with one payer grows 40% week-over-week, that's a new policy that just took effect; catching it in week 2 is worth orders of magnitude more than seeing the cumulative number at month-end.

The second-most-valuable view is first-pass denial rate vs final denial rate by CARC. CARC 16 has a high reverse rate on clean resubmission; CARC 50 does not. Routing workflow that distinguishes recoverable from terminal denials unlocks back-office capacity for the categories with real recovery economics.

Where Vizier fits

Vizier ingests your 835 ERAs through the clearinghouse feed, parses every CARC + RARC + CAS adjustment, joins to the originating claim and provider, and surfaces denial-pattern shifts by payer and code in real time. The dashboard separates the front-end, coding, clinical-documentation, and operational categories so each team gets a workqueue routed to its own scope. Trend lines surface emerging payer policy shifts within 7–14 days of first appearance — which is when the recovery economics matter most.