This is a Claim Adjustment Reason Code (CARC). CARCs explain why a payer adjusted or denied a claim line and appear with a group code (CO, PR, OA, PI). Codes appear on the EOB / ERA after a claim is adjudicated.
Reference only — CARC/RARC are national code sets updated periodically. Verify against the current official list before acting on a denial or appeal.
CARC 45 identifies the amount above an applicable fee schedule, maximum allowable, or contracted rate. Read the group code with it: CO means contractual obligation and assigns that adjustment to the provider, generally as a write-off. Do not transfer a CO-45 amount to the patient. PR assigns patient responsibility, so do not treat every CARC 45 as CO-45.
Check the allowed amount, contract or fee schedule, payer payment, and any separate PR amounts on the remittance. If the allowed amount looks wrong, verify the contract and contact the payer before posting or appealing.
Sources: X12 CARC and group codes ยท CMS remittance guidance. Payer contracts and applicable rules govern the final balance.
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