CO-231: Mutually exclusive procedures
UPDATED JULY 2026 · U.S. PLANS · NOT LEGAL OR MEDICAL ADVICE
Two billed procedures can't be paid together under coding rules. A provider-side coding matter.
CO-231 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-231 denial
- Ask the billing office to review the code pair; a corrected claim or modifier usually resolves it.
- In-network, these write-offs are generally not billable to you.
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