1. Eligibility & Registration Errors
| Code | Reason | Solution |
| CO-16 | Claim lacks info | Resubmit with complete patient/insurance details |
| CO-18 | Duplicate claim | Verify if original claim was processed |
2. Coding Issues
| Code | Reason | Solution |
| CO-4 | Invalid procedure code | Verify CPT®/HCPCS updates |
| CO-50 | Missing/incorrect modifier | Add -25, -59, etc. if justified |
3. Medical Necessity
| Code | Reason | Solution |
| CO-29 | Service not covered | Attach records proving necessity |
| CO-97 | Payer-specific policy | Check LCD/NCD rules |
4. Timely Filing
| Code | Reason | Solution |
| CO-15 | Late submission | Appeal with proof of timely filing |
Pro Tips
✔ Track top 5 denial codes monthly
✔ Use real-time eligibility checks to prevent CO-16/18
✔ Train staff on annual CPT®/ICD-10 updates
