Definition
CARC Code (Claim Adjustment Reason Code)
A standardized code on your EOB that identifies the specific reason your insurance claim was adjusted or denied.
A Claim Adjustment Reason Code (CARC) is a standardized code maintained by the X12 standards organization that appears on your Explanation of Benefits (EOB) to explain why a claim was denied or adjusted. Each code corresponds to a specific denial reason — from medical necessity (CARC 50) to coding issues (CARC 97) to duplicate claims (CARC 18). The CARC code on your EOB is the single most important data point for an insurance appeal because it determines which federal regulations apply, whether the denial is patient-appealable, and what legal argument your appeal letter should make.
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