A denial queue sorted only by date makes everything look equally urgent. Sorting by CARC tells you which team needs to act, whether a corrected claim or an appeal is the right route, and which problems keep coming back for a given clinic.
Educational content from the AiMediCoder editorial team. It is not coding, billing, clinical or legal advice. Code definitions and payer rules change; confirm the current CPT definitions, CMS guidance and each payer's written policy before you bill. Clinic names in examples are fictional.
How to read a denial line
Each adjustment has three parts: a group code (CO, PR or OA), the CARC number, and often a RARC remark code with more detail. The official CARC list, including descriptions and change dates, is maintained by X12. [1] Descriptions below are shortened; use the X12 list for exact wording.
Behavioral health CARC codes and what to do
| Code | Short meaning | Common behavioral health cause | Who acts | Usual route |
|---|---|---|---|---|
| CO-16 | Claim lacks information or has billing errors | Missing rendering NPI, taxonomy, authorization number or referring provider | Billing | Corrected claim |
| CO-50 | Not deemed a medical necessity | Note doesn't support frequency or length (often 90837), or diagnosis not on the payer's list | Clinical reviewer + appeals | Appeal with records, if supported |
| CO-97 | Included in payment for another service | Psychotherapy and another service billed together without the right add-on code or modifier | Coding | Review bundling; correct or appeal |
| CO-197 | Precertification/authorization absent | No auth, expired auth, units used up, or auth number not on the claim | Patient access + billing | Corrected claim or appeal if auth existed |
| CO-29 | Time limit for filing has expired | Late first submission or lost resubmission | Billing / AR | Appeal only with proof of timely filing |
| CO-4 | Procedure code inconsistent with modifier, or modifier missing | Telehealth modifier missing or wrong (95, 93, FQ); a wrong place of service may instead show as CO-5 | Coding / billing | Corrected claim |
| CO-11 | Diagnosis inconsistent with procedure | Diagnosis code doesn't support the service under the payer's policy | Coding + clinician | Review; correct if documentation supports it |
| CO-18 | Exact duplicate claim or service | Resubmitting instead of sending a corrected claim, or a true duplicate | Billing | Check original status; usually no action |
Fix or appeal? A simple rule
- Claim was wrong: send a corrected claim (CO-16, CO-4, many CO-11 and CO-197 cases where the auth number was simply missing).
- Claim was right, payer disagrees: appeal with evidence (CO-50 with a supportive note, CO-197 when the authorization covered the date and units, CO-29 with a clearinghouse acceptance report).
- Nothing to recover: close with a reason (true duplicates, valid contractual adjustments).
Keep corrected-claim and appeal deadlines visible. They are payer-specific and easy to miss in a mixed queue.
A worked example (fictional)
An RCM team managing "Northbend Counseling" sees a week of denials: several CO-197s on 90837, two CO-4s on telehealth claims and one CO-29. Grouping by CARC shows the CO-197s all hit the same plan after a new authorization rule. That is a patient access fix for future visits plus an appeal set for the claims where an authorization was on file. The CO-4s go back to billing to add the plan's modifier. The CO-29 goes to AR to find the clearinghouse acceptance report before deciding whether to appeal.
When the denial says authorization but you know it was approved, our authorization approved, claim denied guide walks through what to compare.
Stopping repeat denials
- Track denials by CARC, payer and clinic every week, not just by dollar amount.
- Name an owner for each CARC group so nothing sits unassigned.
- Turn repeat causes into checks before submission: authorization on the claim, telehealth modifier, documented time for 90834 and 90837.
- Review telehealth setup against each payer's policy; see POS 10 vs 02 and modifier 95.
- Report estimated exposure, potential recovery and confirmed recovered payments as separate figures.
For a wider review across eligibility, documentation and follow-up, use the behavioral health revenue checklist. Terms like 835, CARC and days in AR are in the RCM glossary.
Frequently asked questions
What is a CARC code?
A Claim Adjustment Reason Code (CARC) explains why a claim or service line was paid differently than billed. The list is maintained by X12 and appears on the remittance (835) and EOB.
What is the difference between CARC and RARC?
The CARC gives the main reason for the adjustment. A Remittance Advice Remark Code (RARC) adds detail, such as which piece of information was missing. Read them together.
What does CO mean before the number?
CO is the group code for Contractual Obligation, meaning the adjustment is the provider's responsibility and generally can't be billed to the patient. PR means patient responsibility, OA means other adjustment, and PI means payer-initiated reduction.
What is the most common behavioral health denial code?
There is no single verified answer across all payers. CO-16, CO-197 and CO-50 are frequently discussed in behavioral health, but your own remittance data is the only reliable source for your accounts.
Should every denial be appealed?
No. Many denials, such as CO-16 or CO-4, are fixed with a corrected claim. Appeals make sense when the claim was correct and supported, for example a CO-50 with good documentation or a CO-197 where authorization existed.
Sources
Last reviewed 24 October 2026.
