CO-252 Denial Code: Attachment or Documentation Required
Some services, such as unlisted codes, high-dollar claims, and certain modifiers, require supporting documentation. CARC 252 means the payer is holding or denying the claim until it receives it. Documentation can often be sent electronically by referencing an attachment control number in the claim's PWK segment, or through the payer's portal or fax process.
The group code (CO, PR, OA, PI) tells you who is responsible. The CARC number tells you why.
CO-252 means the payer needs an attachment or other documentation before it can process the claim. The RARC usually identifies what is missing. Send the requested documents through the payer's preferred channel, reference the claim correctly, and follow up until the claim is reprocessed.
Common causes of CO-252.
- Unlisted procedure code without an operative note or description
- Payer requires records for the service or modifier billed
- Documentation was sent but not matched to the claim
- Invoice required for supplies or drugs
How to work a CO-252 denial.
The order matters: confirm the facts before deciding between a corrected claim, a reconsideration, or an adjustment.
- 1Read the RARC and any payer letter to identify exactly what is requested.
- 2Gather only the requested documents and make sure they are signed and dated.
- 3Send them through the payer's preferred channel with the claim number and patient identifiers on every page.
- 4Confirm receipt, then follow up if the claim is not reprocessed within the payer's normal turnaround.
How to keep CO-252 from coming back.
- Identify payers and codes that routinely require documentation and send it with the original claim
- Use the PWK segment and electronic attachments where the payer supports them
Fixing this at the source usually sits with denial management specialists →
Questions about CO-252.
Denials that often travel with this one.
CO-16: Claim Lacks Information or Has Billing Errors
CO-16 means the claim is missing information or has a billing error. How to use the RARC to find what is missing, correct it, and stop it from recurring.
Read about CO-16 →CO-197: Authorization or Precertification Absent
CO-197 means prior authorization, precertification, or notification was missing. How to check for an existing auth, request a retro auth, and prevent it.
Read about CO-197 →CO-50: Not Deemed Medically Necessary
CO-50 means the payer decided the service was not medically necessary. How to review policy and documentation, build an appeal, and handle ABNs for Medicare.
Read about CO-50 →Add a Dedicated Denial Specialist
RCM Staff places trained denial management specialists inside your EHR and clearinghouse to work the queue, correct and appeal claims, and track root causes by payer.
Kevin Jamito has 18+ years of U.S. healthcare revenue cycle management experience across billing, coding, practice management, and offshore RCM operations. He founded RCM Staff to give U.S. healthcare teams dedicated Philippines-based specialists who work inside their existing systems.