CO-251: Incomplete or Deficient Attachment — Information Still Needed

What Does CO-251 Mean?

CO-251 indicates the claim cannot be fully processed because the submitted documentation is incomplete or deficient. This is the provider's contractual responsibility to correct — the patient is not liable for the unpaid amount. The payer received the right type of document but it lacks required content, signatures, or detail needed for adjudication.

CARC 251 sits between CARC 250 (wrong document sent) and CARC 252 (no document sent at all). With CARC 251, the payer received documentation — and it was the right type of document — but the content was incomplete or deficient. Required information is still missing, preventing the payer from adjudicating the claim.

Common deficiencies include incomplete operative notes missing required surgical details, progress notes without required clinical elements, documentation lacking provider signatures or authentication, partially submitted records missing key pages or sections, and scanned documents that are illegible or too low resolution for the payer to read.

This code appears with Group Code CO and must be accompanied by at least one RARC identifying the specific deficiency. The resolution is to complete the deficient documentation and resubmit — this is not a coverage dispute requiring an appeal. In workers' compensation settings, CARC 251 is specifically used when the medical report is incomplete, not in the prescribed format, or otherwise deficient.

Common Causes

How to Resolve

Identify the specific documentation deficiency using the RARC codes, complete the missing information, and resubmit.

1. Identify the deficiency Review the RARC codes to understand exactly what is missing or deficient. Compare the submitted document against the payer's documentation requirements checklist.
2. Retrieve missing information Contact the appropriate clinical department to obtain the missing elements — signatures, complete notes, additional report sections, or higher-quality scanned copies.
3. Verify completeness before resubmission Before resubmitting, verify that all identified deficiencies have been corrected. Run through the payer's documentation checklist to ensure nothing else is missing.
4. Resubmit the corrected claim Submit the claim with the completed documentation properly linked to the original claim reference. Ensure documents are legible and in the correct format.
5. Monitor for processing Track the claim after resubmission to ensure it processes correctly and no additional documentation deficiencies are identified.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-251:

How to Prevent CO-251

• Implement documentation completeness checklists that verify all required elements are present before submitting attachments
• Ensure all documentation includes required provider signatures, dates, and authentication before submission
• Verify scanned documents are legible and at sufficient resolution for payer processing — minimum 300 DPI recommended
• Train clinical staff on payer-specific documentation format requirements and required note elements
• Conduct pre-submission quality reviews on attachments to catch incomplete or deficient records before they trigger denials
• Maintain direct communication channels with payers to clarify documentation requirements when uncertain

General Prevention

• Implement documentation completeness checklists that verify all required elements are present before submitting attachments to payers
• Ensure all submitted documentation includes required signatures, dates, and authentication before sending
• Verify that scanned documents are legible and at sufficient resolution for the payer's processing requirements
• Familiarize billing staff with payer-specific documentation format requirements and templates
• Conduct pre-submission quality checks on attachments to identify incomplete or deficient records before they trigger denials

Related Denial Codes