CO-163: Attachment/Documentation Referenced on Claim Not Received
Provider responsibility — correct and resubmit to the appropriate payer. The patient is not liable for this amount.
What Does CO-163 Mean?
With CO (Contractual Obligation), the CARC 163 adjustment for attachment/documentation referenced on claim not received indicates the claim needs to be corrected or routed to a different payer. The patient is not liable for this amount. Correct the issue and resubmit.
CARC 163 is used when the payer determines that attachment/documentation referenced on claim not received. The claim could not be processed as submitted because required information was absent, incomplete, or did not meet the payer's submission standards.
Common scenarios that trigger this adjustment include: the claim indicated that supporting documentation was attached, but the payer did not receive the referenced attachment with the electronic or paper claim; The documentation was sent separately from the claim and was lost, misfiled, or not linked to the claim during payer processing; The attachment control number on the claim does not match the control number on the submitted documentation, preventing the payer from linking them. The group code paired with CARC 163 determines who bears the financial responsibility — CO places it on the provider as a contractual obligation, OA indicates a coordination of benefits or other payer adjustment, PR shifts it to the patient.
Common Causes
| Cause | Frequency |
|---|---|
| Referenced attachment not included with claim submission The claim indicated that supporting documentation was attached, but the payer did not receive the referenced attachment with the electronic or paper claim | Most Common |
| Attachment lost in transit or processing The documentation was sent separately from the claim and was lost, misfiled, or not linked to the claim during payer processing | Most Common |
| Incorrect attachment control number The attachment control number on the claim does not match the control number on the submitted documentation, preventing the payer from linking them | Common |
| Electronic attachment submission failure The electronic attachment transmission failed or was rejected, but the claim was processed without the attachment | Common |
| Attachment sent to wrong address or department The supporting documentation was sent to an incorrect payer address, fax number, or department, preventing it from being associated with the claim | Common |
How to Resolve
- Review the denial reason Examine the CO-163 adjustment and any RARC codes to identify what needs to be corrected.
- Correct the claim Address the issue that triggered the denial — update the claim with correct information or route to the appropriate payer.
- Resubmit the claim Submit the corrected claim per the payer's guidelines.
This denial indicates the payer did not receive the referenced attachment. Resubmit the documentation with the correct claim reference number rather than filing an appeal. If you have proof the documentation was previously sent, contact the payer to request reprocessing.
Common RARC Pairings
The RARC code tells you exactly what triggered the CO-163:
| RARC | Description |
|---|---|
| M127 | Missing/incomplete/invalid documentation/orders/notes Submit the referenced documentation with the correct claim attachment control number → |
| N130 | You may need to review plan documents or guidelines Review the payer's attachment submission requirements and resubmit documentation → |
How to Prevent CO-163
- Verify that all referenced attachments are included before submitting claims
- Use electronic attachment submission methods when available for reliable delivery tracking
- Confirm attachment control numbers match between the claim and supporting documentation
- Maintain proof of submission for all attachments sent separately from claims
- Verify the payer's correct address, fax number, or portal for receiving attachments
- Follow up with the payer to confirm receipt of attachments within 5-7 business days of submission
Also Filed As
The same CARC 163 may appear with different Group Codes:
Related Denial Codes
Sources
- https://www.mdclarity.com/denial-code/163
- https://www.arlearningonline.com/2019/12/163-attachmentother-documentation.html
- https://x12.org/codes/claim-adjustment-reason-codes
- https://portal.ct.gov/-/media/ohs/health-it-advisory-council/apcd-advisory-group/data-submission-guide-workgroup/meeting-materials/6-30-22/carc-codes_final.pdf
- Codes maintained by X12. Visit x12.org for official definitions.