CO-18
Duplicate claim or service
What This Code Means
The payer’s system identified this claim or service line as a duplicate of one already submitted and processed.
Common Causes
- Claim resubmitted before the original finished processing
- Same service billed by two different staff members
- Clearinghouse submitted the batch twice
- Corrected claim submitted without the required frequency code
How to Resolve or Appeal
- Pull the original claim's status before resubmitting anything
- If it truly is a duplicate, no action needed — do not resubmit
- If it's a correction, use frequency code 7 (replacement) or 8 (void) on the 837
- Call the payer if the original claim shows no record on their end
Educational reference only — not medical or legal advice. Always confirm code usage and appeal rights with the specific payer.