Healthcare Error Code
Healthcare Insurance / Medical Billing
Claim Adjustment Reason Codes (CARC)
CO-21 | Missing/invalid place of service
Industry
Healthcare
Canonical
/healthcare/error-codes/co-21/
Last Updated
Feb 25, 2026
Summary
This code indicates that the place of service information was missing or invalid on the claim.
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What This Code Means
CO-21 is applied when the place of service code does not meet payer requirements. Place of service identifies where care was provided and affects reimbursement. Incorrect or missing values prevent accurate adjudication. This is a data validation issue rather than a coverage decision. The service may be eligible once corrected.
Where Users Usually See This Code
- Claim rejection notices
- Remittance advice
- Claim status portals
Why This Code Appears
- Place of service code missing
- Invalid or outdated place of service value
- Payer-specific service location rules
What Typically Happens Next
- Claim processing is halted
- Reprocessing may be required
- Payment is delayed
What This Code Is Not
- It is not a coverage denial
- It is not a contractual adjustment
- It is not patient responsibility
Troubleshooting Checklist
- □ Verify place of service codes
- □ Review payer location requirements
- □ Confirm claim data accuracy
Notes And Edge Cases
Place of service requirements may differ by payer and program. Certain services are reimbursed differently depending on location.
Related Codes
8 links
- CO-16 CodeClaim lacks required information
- CO-125 CodeSubmission/billing error
- CO-133 CodeIncorrect provider type
- CO-33 CodeInsufficient documentation
- CO-62 CodeNot covered for place of service
- CO-178 CodeClaim did not contain sufficient information
- CO-197 CodePrecertification required
- CO-23 CodeImpact of prior payer adjudication
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