CO-16: Claim/Service Differs from Information on File
CO (Contractual Obligation)What is CO-16?
CO-16 is a Contractual Obligation adjustment code indicating the claim or service submitted differs from information the payer has on file. UnitedHealthcare pairs this code with RARC N2 in the majority of denials involving missing modifier 25.
Why Does CO-16 Occur?
- Missing or incorrect modifier. The claim needs modifier 25 to distinguish the E/M service from the procedure, but it was omitted.
- Quantity mismatch. The submitted quantity differs from the payer's prior authorization.
- Procedure code variation. The claim shows one CPT code but the payer has a different code from the prior visit on file.
- Place of service mismatch. The claim shows office (11) but the payer's prior auth specifies telehealth (02).
How to Fix CO-16 Denials
- Pull the original claim and the payer's EOB side by side. Identify which field the payer flags as different: modifier, quantity, procedure code, or place of service.
- Cross-check against the prior authorization. If the discrepancy is a modifier, add modifier 25 and resubmit. If quantity or code changed, confirm it matches the auth.
- Document the fix in your AR system with the specific field corrected and the justification.
- Resubmit as a corrected claim within 30 days.
- If the resubmission is denied again, file a formal appeal with supporting documentation. Commercial payers allow 60-365 days to appeal.
CO-16 by Payer
| Payer | Common RARC | Appeal Deadline | Notes |
|---|---|---|---|
| UnitedHealthcare | N2 | 60 days from remittance | Modifier 25 is the fix in most CO-16 denials. |
| Anthem | N3 | 365 days from denial notice | Check payer portal for prior auth details before resubmitting. |
| Aetna | N2 | 180 days from denial | Often pairs with CO-97. Verify E/M level separately. |
| Cigna | N357 | 180 days from denial | Prior auth mismatch is the primary cause. Search by date of service. |
| Medicare | Varies | 120 days (redetermination at MAC) | Verify claim matches CMS-1500 submission standards. |
Related CARC Codes
If you are seeing CO-16, check these related codes: CO-97 (bundled service denial), CO-4 (incompatible coding), CO-22 (coordination of benefits).
Related CPT Modifiers
Modifier 25 (Distinct Procedural Service).
Common Questions About CO-16
Does CO-16 always mean a missing modifier?
No. CO-16 covers any field mismatch between the submitted claim and payer records: modifier, quantity, procedure code, or place of service. Check the RARC code on the EOB to identify the specific discrepancy.
Can I appeal a CO-16 denial?
Yes. Commercial payers allow 60-365 days depending on the plan. Include documentation showing the corrected field and why the original submission was valid or the correction is warranted.
What is the difference between CO-16 and CO-97?
CO-16 means the claim differs from what the payer has on file. CO-97 means the service is bundled or not separately payable. CO-16 is a data mismatch; CO-97 is a coverage rule.
Altair catches CO-16 denials before submission with pre-claim modifier validation. See how pre-submit claim scoring works.