Attachment or documentation required
The payer needs records or another document before it can decide this claim.
CO = Contractual Obligation. The provider owes the difference. The patient cannot be billed for this amount. The same reason code can appear with a different group code; the group decides who may be billed.
Usual causes
- Unlisted or by-report code without a description or report (N350).
- High-dollar claim, modifier 22 or a service the payer always reviews.
- Claim references an attachment (PWK) that never arrived.
The fix
Send the requested documentation with the claim number by the payer's method (portal upload, fax with the attachment control number, or mail). Keep proof. If the payer requires the records on first submission, set up a workflow for that code.
Appeal or corrected claim?
Send the documentation (reopening or resubmission with attachment), not an appeal.
Deadline to watch
Respond within the payer's request window (often 30 to 45 days) and inside timely filing.
Exact limits are in your payer contract or provider manual. When in doubt, send the correction or appeal this week.
CO-252 in short
What does CO-252 mean?
The payer needs records or another document before it can decide this claim. The official X12 text reads: "An attachment/other documentation is required to adjudicate this claim/service. At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT)."
What usually causes a CO-252 denial?
Unlisted or by-report code without a description or report (N350). High-dollar claim, modifier 22 or a service the payer always reviews. Claim references an attachment (PWK) that never arrived.
How do I fix CO-252?
Send the requested documentation with the claim number by the payer's method (portal upload, fax with the attachment control number, or mail). Keep proof. If the payer requires the records on first submission, set up a workflow for that code.
Should I appeal CO-252 or send a corrected claim?
Corrected claim. Send the documentation (reopening or resubmission with attachment), not an appeal.
What deadline applies to CO-252?
Respond within the payer's request window (often 30 to 45 days) and inside timely filing.