CO-23 Denial Code Explained

CO-23 is a medical billing denial code that indicates payment has been adjusted because another payer has already made payment on the claim. This denial commonly occurs when multiple insurance plans are involved and coordination of benefits rules apply.

What Does CO-23 Mean?

The CO-23 denial code means the insurance payer reduced or adjusted payment because another payer has already paid all or part of the claim.

This denial is often related to coordination of benefits, secondary insurance claims, and payer sequencing issues.

Common Reasons for CO-23

• Another insurance company already paid the claim

• Incorrect primary and secondary payer order

• Coordination of benefits errors

• Duplicate payment records

• Medicare Secondary Payer (MSP) issues

• Incorrect insurance information on file

How To Fix CO-23

Review the explanation of benefits from all insurance carriers involved and determine which payer has primary responsibility. Verify coordination of benefits information and ensure the claim was submitted in the correct order.

If payment information appears incorrect, contact the payer and provide supporting documentation showing the payment history.

Frequently Asked Questions

What does CO-23 mean?

CO-23 means another payer has already made payment on the claim and the current payer adjusted reimbursement accordingly.

Is CO-23 related to coordination of benefits?

Yes. Coordination of benefits issues are one of the most common causes of CO-23 denials.

Can CO-23 be appealed?

Yes. If payment information is inaccurate or the adjustment was applied incorrectly, providers may request a review.

What should I review first?

Review all payer explanations of benefits and verify the correct primary and secondary payer sequence.

Can Medicare claims receive a CO-23 denial?

Yes. Medicare Secondary Payer rules can result in CO-23 adjustments when another insurance carrier has already issued payment.

Related Denial Codes

You may also encounter:

• CO-20 — Another payer is primary

• CO-21 — Charges covered under a capitation agreement

• CO-22 — Coordination of benefits issue

• CO-109 — Claim not covered by this payer

Quick Summary

CO-23 indicates another payer has already made payment on the claim. Most denials are caused by coordination of benefits issues, payer sequencing errors, or incorrect insurance information.