Official CARC description: “Exact duplicate claim/service.” Here’s what it actually means, why it fires, and how to get the claim paid.
OA-grouped duplicate — same playbook as CO 18: find the original, decide if this copy ever needed to exist, and fix the workflow that produced it.
Liability group: OA = Other Adjustment — neither clearly provider nor patient liability — most often coordination-of-benefits math or duplicates. Usually informational; verify before writing anything off.
Locate and work the ORIGINAL claim's status
Repeat services: modifier 76/77/91 on a corrected claim
Kill auto-rebill timers shorter than payer adjudication cycles
Medicare crossovers: wait for the crossover before billing secondaries directly
Appeal only false duplicates with distinct-service proof — otherwise the original claim is where the work is.
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: OA-grouped duplicate — same playbook as CO 18: find the original, decide if this copy ever needed to exist, and fix the workflow that produced it.
OA stands for Other Adjustment — neither clearly provider nor patient liability — most often coordination-of-benefits math or duplicates. Usually informational; verify before writing anything off.
Appeal only false duplicates with distinct-service proof — otherwise the original claim is where the work is.