CO-18 denial: Duplicate claim
The payer says this claim or service duplicates one it already received.
Common causes
- The same claim was submitted twice, for example after a slow acknowledgement
- Staff resubmitted instead of checking the status of the first claim
- A genuine repeat service was billed without anything to tell it apart
How to fix it
- Look up the first claim; it may already be paid or in process
- If it was paid, post the payment and do nothing further
- For a genuine repeat service, correct the claim with the appropriate modifier and documentation
How to prevent it
- Check claim status before resubmitting
- Set a rule for how long to wait before any follow-up on an unacknowledged claim
Zenith billers and AR specialists work denials like this inside your practice-management system, and your practice stays the billing provider. See AR follow-up and medical billing.
Educational summary, not billing or legal advice. Payer rules and deadlines vary; always check the payer’s own policy and the remark code on your remittance.