CO-252: Attachment Required to Adjudicate Claim
CO-252 means you need to submit missing documentation. Gather the required attachments identified by the RARC codes and resubmit the claim.
What Does CO-252 Mean?
When paired with Group Code CO, the missing documentation is a contractual obligation between the provider and payer. The payer cannot process the claim without the required attachments, and the provider is responsible for supplying them. The adjustment amount cannot be collected from the patient.
CARC 252 signals that the payer received your claim but cannot complete adjudication because supporting documentation is missing. This is not a coverage determination or a judgment on medical necessity — the payer simply needs more information before it can make a payment decision.
The specific documentation needed varies by payer and service type. Common examples include clinical notes, operative reports, test results, prior authorization letters, or Explanation of Benefits from a primary payer. The accompanying RARC codes on the remittance advice are critical because they pinpoint exactly which documents the payer is requesting.
This code appears frequently on claims for services that commonly require attachments, such as complex procedures, services requiring prior authorization documentation, or secondary claims needing the primary payer's EOB. Tracking patterns of CARC 252 denials by payer can reveal systematic documentation gaps in your billing workflow.
Common Causes
| Cause | Frequency |
|---|---|
| Required supporting documentation not submitted with claim The payer requires specific attachments to process the claim such as clinical notes, test results, medical records, or operative reports and none were submitted with the original claim | Most Common |
| Prior authorization documentation missing The claim requires documentation of prior authorization approval but the authorization letter, reference number, or supporting clinical documentation was not included with the submission | Common |
| Medical necessity documentation not provided The payer requires documentation demonstrating medical necessity for the service such as a letter of medical necessity, clinical evaluation, or diagnostic test results and none was submitted | Common |
| Coordination of Benefits documentation missing The payer needs COB information or an Explanation of Benefits from the primary insurer to process the claim as secondary and the required EOB was not attached | Common |
| Payer-specific attachment requirements not met Different payers have different documentation requirements and the provider did not meet the specific payer's attachment mandates for the type of service billed | Common |
How to Resolve
- Identify missing documentation from RARC codes Review the remittance advice for accompanying RARC codes such as N479, N710, N712, N714, or N716 to determine exactly which documents the payer requires.
- Gather required attachments Collect clinical notes, test results, prior authorization documentation, primary payer EOBs, or other materials specified by the RARC codes.
- Contact the payer if needed If no RARC accompanies the denial or the documentation requirement is unclear, contact the payer to confirm what specific attachments are needed.
- Submit attachments and resubmit claim Send the required documentation via the payer's electronic attachment process or portal, and resubmit the corrected claim.
- Monitor and follow up Track the resubmitted claim status and follow up within the expected processing timeframe if no response is received.
CO-252 indicates the payer needs additional documentation to process the claim. This is a documentation request, not a coverage dispute. Submit the required attachments identified by the accompanying RARC codes and resubmit the claim rather than filing an appeal.
Common RARC Pairings
The RARC code tells you exactly what triggered the CO-252:
| RARC | Description |
|---|---|
| N479 | Missing Explanation of Benefits (Coordination of Benefits or Medicare Secondary Payer) Submit the primary payer's EOB and resubmit the claim → |
| N710 | Missing clinical notes Submit the clinical notes for the date of service → |
| N712 | Missing summary documentation Submit the required summary report → |
| N714 | Missing medical report Submit the specific medical report requested → |
| N716 | Missing chart documentation Submit the patient's chart for the date of service → |
How to Prevent CO-252
- Identify payer-specific attachment requirements for each service type before claim submission and include all required documentation upfront
- Build attachment requirement checklists into the billing workflow to ensure clinical notes, test results, and authorization documents are gathered before claims are generated
- Verify prior authorization documentation is complete and included with claims that require it
- Implement automated alerts in the billing system when claims for services that commonly require attachments are submitted without documentation
- Track CO-252 denial patterns by payer to identify systematic documentation gaps and proactively address them
- Maintain current Coordination of Benefits information and include primary payer EOBs when billing as secondary
Also Filed As
The same CARC 252 may appear with different Group Codes:
Related Denial Codes
Sources
- https://etactics.com/blog/denial-code-co-252
- https://www.mdclarity.com/denial-code/252
- https://hcmsus.com/blog/co-252-denial-code
- https://x12.org/codes/claim-adjustment-reason-codes
- Codes maintained by X12. Visit x12.org for official definitions.