CommonContractual Obligation (CO)Duplicate Claim
CO-18: Duplicate claim/service
The payer has identified this claim or service line as a duplicate of a previously submitted and adjudicated claim. This means the exact same service for the same patient on the same date of service has already been processed.
Common Causes
- Claim was accidentally submitted more than once
- Corrected claim was submitted without proper replacement indicator
- Different staff members submitted the same claim independently
- System error caused automatic resubmission
- Claim was resubmitted after an initial rejection without correcting the frequency code
How to Resolve CO-18
- 1Verify whether the original claim was paid -- if so, no action needed
- 2If this is a corrected claim, resubmit with frequency code 7 (replacement) and the original claim number
- 3If the services are legitimately separate (e.g., bilateral procedures), add appropriate modifiers and appeal
- 4If truly a duplicate, write off the denied claim
How to Prevent CO-18 Denials
- Track claim submission status to prevent accidental resubmission
- Use frequency code 7 (replacement) or 8 (void) when resubmitting claims
- Implement a claim tracking system that flags potential duplicates before submission
- Establish clear workflows for corrected claims vs. new submissions
Related Denial Codes
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