CO-16: Claim lacks information or has a submission error
UPDATED JULY 2026 · U.S. PLANS · NOT LEGAL OR MEDICAL ADVICE
Something required is missing from the claim itself — an identifier, a date, an attachment. The accompanying remark codes (usually starting with M or N) say exactly what.
CO-16 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-16 denial
- Read the remark codes on the notice for the specific missing item.
- Ask the billing office to supply it and resubmit — this usually doesn't need a formal appeal.
- Watch the timely-filing clock: corrected claims still have deadlines.
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