CARC (Claim Adjustment Reason Code)
A standardized code on a remittance that explains why a payer adjusted or denied a claim line.
CARCs tell you what the payer flagged - for example, a coverage or medical-necessity issue. They're the starting point for denial triage, but the code alone doesn't give the root cause; that requires looking at the claim.
CARCs are paired with RARCs for more detail.