Official CARC description: “Exact duplicate claim/service.” Here’s what it actually means, why it fires, and how to get the claim paid.
The payer already has this claim. Real duplicates need no action — but “false duplicates” (legitimate repeat services on the same day) and stuck originals hide underneath this code.
Liability group: CO = Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Locate the ORIGINAL claim's status first — that decides everything
Legit repeat service: corrected claim with modifier 76/77/91 or RT/LT
Correcting a claim: resubmit with frequency 7 + original claim number
Original mishandled: work THAT claim; another copy just re-denies
Appeal only the false-duplicate case: show the two services were distinct (times, sites, repeat-test rationale) with the right modifier on a corrected claim.
Fill in the denial facts — use placeholders, never real patient data (the letter keeps [PATIENT NAME]-style fields so you can merge real details privately). A payer-ready draft with an enclosure checklist comes back in ~20 seconds.
Your appeal letter draft will appear here.
Exact duplicate claim/service. In practice: The payer already has this claim. Real duplicates need no action — but “false duplicates” (legitimate repeat services on the same day) and stuck originals hide underneath this code.
CO stands for Contractual Obligation — the provider absorbs it — the amount cannot be billed to the patient. If the denial is wrong, the money is recovered by correcting or appealing the claim, not by balance-billing.
Appeal only the false-duplicate case: show the two services were distinct (times, sites, repeat-test rationale) with the right modifier on a corrected claim.