CO-252: Attachment or documentation required
UPDATED JULY 2026 · U.S. PLANS · NOT LEGAL OR MEDICAL ADVICE
The payer wants supporting records before deciding — not a denial on the merits yet.
CO-252 at a glance
- Code group: CO — Contractual Obligation — in-network providers generally cannot bill you for CO adjustments.
- Who usually fixes it: The provider’s billing office.
- Worth appealing? Rarely — usually fixed by resubmission.
What to do about a CO-252 denial
- Ask the billing office to send the requested documentation promptly.
- Track the claim afterward; a merits decision (and appeal rights) comes after review.
Denied? Don’t drop it
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