CO-16: Claim/service lacks information or has submission/billing error(s).
The claim is missing required information or has a data or billing error that prevents adjudication. Code 16 is a header level flag that must be paired with a remark code telling you exactly what field or documentation is missing. Without checking that remark code you cannot fix this denial.
What the group code means
- CO
- Contractual Obligation. The provider is responsible and the amount cannot be billed to the patient.
This CARC is reported under more than one group code depending on the payer and the circumstances: CO, PI.
Why it fires
- A required field on the claim was blank, invalid, or inconsistent, such as a missing NPI or invalid diagnosis pointer
- The payer's system flagged a data mismatch between the 837 claim and its records
- Supporting documentation required for this code type was not attached
Corrective actions, ranked
- 1
Read the paired remark code first
Always check the accompanying RARC before doing anything else. Code 16 alone does not tell you what is wrong.
- 2
Correct and resubmit
Fix the specific field or error identified by the remark code and resubmit as a corrected claim, not an appeal.
- 3
Audit your claim scrubber rules
If this recurs across many claims, add a pre-submission edit check for the specific field that keeps failing.
Is it worth appealing
Not an appeal candidate. This is a correctable data error, so fix and resubmit a corrected claim rather than filing a formal appeal.
Remark codes that arrive with it
A RARC carries the detail behind CO-16. These are the ones our dataset records alongside it.
Other denial codes to check
Codes that share a remark code with this one, or that are reported under the same group code.
- CO-45Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.
- CO-97The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated.
- CO-11The diagnosis is inconsistent with the procedure.
- OA-18Exact duplicate claim/service (Use only with Group Code OA except where state workers' compensation regulations requires CO)
- CO-29The time limit for filing has expired.
- PR-151Payment adjusted because the payer deems the information submitted does not support this many/frequency of services.
Retrieved 2026-07-18.
Do not let this happen again
Scrub the claim against NCCI PTP and MUE edits before you submit, free and in your browser.
Denial7 provides billing and administrative guidance based on published CMS and X12 sources. It is not medical advice, not a coverage determination, and not a guarantee of payment. NCCI and MUE edits are republished quarterly and payer policies vary by contract. Always confirm against the payer's own current policy before submitting or appealing.