CO-252 Denial Code: Documentation Required to Process the Claim
The CO-252 denial code means the payer needs an attachment or additional documentation before it can finish adjudicating the claim. It is a request, not a final coverage decision - the claim is parked until you supply what was asked for. The accompanying remark code usually specifies what to send: operative notes, invoices for drugs or devices, medical records, or a required certificate.
Common Causes
- High-dollar, unlisted, or miscellaneous codes (including not-otherwise-classified drug codes) billed without the invoice or description the payer requires
- Services under prepayment review where records must accompany every claim
- Modifier usage (like 22 for increased procedural services) that requires an operative note to support extra payment
- The payer's documentation request letter went unanswered within its deadline
How to Fix CO-252
- Read the remark codes and any development letter to identify exactly which document the payer wants
- Send the requested documentation through the payer's specified channel (portal upload, fax with the request cover sheet, or paper) and reference the claim number
- For unlisted and NOC codes, include a clear description, invoice, and comparison code in the claim narrative on future submissions
- Respond inside the payer's deadline - unanswered requests convert into final denials
- Track which codes trigger documentation requests and attach the records proactively on those claims
Frequently Asked Questions
CO-252 means an attachment or other documentation is required before the payer will adjudicate the claim - commonly operative notes, invoices for unlisted or NOC-coded items, or medical records for services under review.
Identify the requested document from the remark codes or the payer's letter, submit it through the payer's specified channel referencing the claim, and do it within their deadline. The claim resumes processing once the documentation is received - no formal appeal is usually needed at this stage.
Related Denial Codes
Related Resources
Claim adjustment reason codes and remittance advice remark codes are standardized code sets maintained by X12. The explanations on this page are written in our own words for educational purposes, based on public CMS and Medicare contractor documentation. Payer policies vary - always confirm handling with the specific payer's guidance and your contracts.