Healthcare Error Code
Healthcare Insurance / Medical Billing
Claim Adjustment Reason Codes (CARC)
CO-66 | Incomplete procedure code
Industry
Healthcare
Canonical
/healthcare/error-codes/co-66/
Last Updated
Feb 25, 2026
Summary
This code indicates that the procedure code submitted was incomplete or improperly formatted.
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What This Code Means
CO-66 is used when a procedure code lacks required components. Complete codes are necessary for payer adjudication. This is a formatting and completeness issue rather than a coverage determination. The service may be eligible once a complete code is submitted.
Where Users Usually See This Code
- Claim rejection messages
- Remittance advice
- Coding validation reports
Why This Code Appears
- Truncated or partial procedure codes
- Missing required code digits
- Submission formatting errors
What Typically Happens Next
- Claim is rejected or denied
- Reprocessing may be required
- Payment is delayed
What This Code Is Not
- It is not a non-covered service
- It is not a duplicate claim
- It is not a contractual adjustment
Troubleshooting Checklist
- □ Review procedure code completeness
- □ Confirm submission formatting
- □ Monitor coding system updates
Notes And Edge Cases
Electronic systems may automatically reject incomplete codes. Code length requirements vary by coding system.
Related Codes
8 links
- CO-16 CodeClaim lacks required information
- CO-65 CodeProcedure code invalid
- CO-22 CodeCare may be covered by another payer
- CO-62 CodeNot covered for place of service
- CO-133 CodeIncorrect provider type
- CO-18 CodeDuplicate claim/service
- CO-27 CodeCoverage terminated
- CO-61 CodeProcedure not covered for age
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