EOB denial code CO-16: what it means

What it means

The claim is missing required information or contains a billing error, so the insurer could not finish processing it. A Remittance Advice Remark Code (an N- or M- code) usually appears alongside this one to say exactly what is missing.

Contractual Obligation — an adjustment the provider agreed to by contract. The patient is generally not billed for CO amounts.

Official X12 description

“Claim/service lacks information or has submission/billing error(s)”

Typical cause

Incomplete or incorrect claim data — a missing field, an invalid code, or absent documentation flagged by an accompanying remark code.

What to do next

1. 1Look for the RARC remark code listed next to CO-16 on your EOB; it names the specific missing item.
2. 2Share that detail with your provider's billing office so they can correct and resubmit.
3. 3This is usually corrected by the provider, not paid by the patient.