CARC: Claim Adjustment Reason Code
CARCs are the X12-standard codes payers use on the 835 ERA to explain every adjustment or denial on a claim line. CARC analytics surface the front-end and back-end workflow gaps that drive lost revenue.
What is a CARC?
CARCs (Claim Adjustment Reason Codes) are maintained by the X12 / Washington Publishing Company committee and used by every US healthcare payer. Each adjustment on the 835 Electronic Remittance Advice carries a CARC plus a Claim Adjustment Group Code (CO contractual, PR patient responsibility, OA other, PI payer-initiated, CR correction). The CARC tells you why the payer reduced or denied the line.
The five highest-impact CARCs at most practices
- CARC 197 — Precertification / authorization absent. Front-end workflow gap: the auth wasn't obtained before service. Appeals are uphill.
- CARC 16 — Claim/service lacks information. Documentation incomplete; payer doesn't say which field is missing.
- CARC 18 — Duplicate claim/service. Almost always a clearinghouse routing or resubmission workflow issue, not a real duplicate.
- CARC 109 — Claim not covered by this payer. Eligibility verification gap: the patient's coverage doesn't match what was billed.
- CARC 50 — Medical necessity not met. Service was performed but documentation or payer policy doesn't support coverage.
Why CARC 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.
CARC vs RARC
CARCs explain the adjustment. RARCs (Remittance Advice Remark Codes) provide additional explanatory detail. A single line can carry one CARC and multiple RARCs. The CARC tells you what category of issue you're looking at; the RARC narrows it to the specific cause. Analytics teams typically cluster on CARC for trend analysis and on RARC for root-cause routing to the right workflow team.