Behavioral Health Denial Codes: CARC List, Group Codes & First Fixes (2026)
A denial on an ERA or EOB arrives as a string like CO-197 or PR-96 with a remark code next to it. Each piece answers a different question: who owes the balance, why the payer adjusted it, and what exactly to fix. Here are the codes behavioral health claims get most, with what they usually mean on a therapy, psychiatry, or SUD claim.
Short answer
A denial code has two parts: a group code (CO, PR, OA, or PI) that says who owes the balance, and a Claim Adjustment Reason Code (CARC) that says why. The CARCs behavioral health claims get most are 16 (missing information), 197 (no authorization), 96 (non-covered), 50 (medical necessity), 252 (documentation required), 4 and 11 (code mismatches), 29 (timely filing), 22 and 109 (wrong payer), and 18 (duplicate). The remark code (RARC) beside it names the specific problem.
Read the code in three parts
Take CO-16 with remark N290. CO is the group code: the provider owes the adjusted amount and can't bill the patient for it. 16 is the reason: the claim lacks information. N290 is the remark: the rendering provider's NPI is missing or invalid. The remark is what tells you what to fix.
| Group code | Name | Who owes the adjusted amount |
|---|---|---|
| CO | Contractual Obligation | The provider. Don't bill the patient. |
| PR | Patient Responsibility | The patient, under their plan: deductible, coinsurance, copay, or a non-covered service. |
| OA | Other Adjustment | Neither, by contract or patient liability. Common on duplicates and crossover claims. |
| PI | Payer Initiated Reductions | The provider, when the payer believes no contract applies. Not used by Medicare. |
The CARCs behavioral health claims get most
| CARC | Official wording | What it usually means in behavioral health | First move |
|---|---|---|---|
| 16 | “Claim/service lacks information or has submission/billing error(s).” | A field is missing or wrong: rendering NPI, taxonomy, modifier, place of service, diagnosis, or member ID. | Read the remark code, correct the field, resubmit. |
| 197 | “Precertification/authorization/notification/pre-treatment absent.” | No authorization on file for IOP, PHP, residential, psych testing, or a Medicaid service that needs one. | Find the auth number or request a retro-authorization. |
| 96 | “Non-covered charge(s).” | The plan or contract doesn't cover the service: couples counseling, a provider type, audio-only. | Check the remark code and group code to see who owes it. |
| 50 | “These are non-covered services because this is not deemed a 'medical necessity' by the payer.” | The record doesn't support the service or level of care: 90837 length, IOP, or ongoing weekly therapy. | Appeal with the treatment plan, assessments, and progress. |
| 252 | “An attachment/other documentation is required to adjudicate this claim/service.” | Records requested before payment, often on 90837, crisis codes, or high-frequency services. | Send the named records through the payer's attachment channel. |
| 4 | “The procedure code is inconsistent with the modifier used.” | Missing or wrong telehealth (95, 93) or licensure (HO, HN, AJ) modifier. | Fix the modifier. See modifiers. |
| 11 | “The diagnosis is inconsistent with the procedure.” | A Z code as primary, or a diagnosis the payer doesn't accept for the service. | Bill a supported ICD-10 code first. |
| 97 | “The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated.” | Two services the same day that bundle, such as an evaluation and psychotherapy. | Check same-day pairs before billing. |
| 151 | “Payment adjusted because the payer deems the information submitted does not support this many/frequency of services.” | More sessions per week or per day than the policy allows. | Appeal with clinical justification, or adjust frequency. |
| 170 | “Payment is denied when performed/billed by this type of provider.” | A provider type the plan doesn't pay for this service, such as an associate. | See associate billing. |
| 185 | “The rendering provider is not eligible to perform the service billed.” | Credentialing gaps, or a therapist billing a prescriber-only code like 90792. | Check credentialing and the code's provider rules. |
| B7 | “This provider was not certified/eligible to be paid for this procedure/service on this date of service.” | Service before the credentialing effective date. | Ask for a retro effective date, or write off. |
| 29 | “The time limit for filing has expired.” | Late first submission. Medicare allows 12 months from the date of service; others set their own limit. | Appeal only with proof of timely filing. |
| 18 | “Exact duplicate claim/service” | The same claim sent twice, often after a corrected claim went in as new. | Use the corrected-claim frequency code instead. |
| 22 | “This care may be covered by another payer per coordination of benefits.” | The payer thinks another plan is primary. | Update COB with the patient and bill the primary. |
| 109 | “Claim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor.” | A behavioral health carve-out: the medical plan isn't the behavioral health payer. | Find the carve-out. See eligibility denials. |
| 27 | “Expenses incurred after coverage terminated.” | Coverage ended, common with Medicaid redeterminations. | Re-verify eligibility, then bill the right coverage. |
The remark codes that tell you what to fix
CARCs 16, 96, and 252 always come with at least one remark code. These are the ones that appear most on behavioral health remittances.
| RARC | Wording | Seen with |
|---|---|---|
| M51 | Missing/incomplete/invalid procedure code(s). | CO-16 |
| M76 | Missing/incomplete/invalid diagnosis or condition. | CO-16 |
| M77 | Missing/incomplete/invalid/inappropriate place of service. | CO-16, telehealth POS 02 vs 10 |
| N290 | Missing/incomplete/invalid rendering provider primary identifier. | CO-16, associates and new clinicians |
| N382 | Missing/incomplete/invalid patient identifier. | CO-16, Medicaid ID changes |
| N822 / N823 | Missing procedure modifier(s). / Incomplete/Invalid procedure modifier(s). | CO-16, CO-4 |
| MA130 | Your claim contains incomplete and/or invalid information, and no appeal rights are afforded… | CO-16: fix and resubmit, don't appeal |
| N54 | Claim information is inconsistent with pre-certified/authorized services. | CO-197, auth on file for a different code or provider |
| N95 | This provider type/provider specialty may not bill this service. | CO-96, CO-170 |
| N130 | Consult plan benefit documents/guidelines for information about restrictions for this service. | PR-96, CO-96 |
| N425 | Statutorily excluded service(s). | CO-96 and PR-96 on Medicare |
| M127 | Missing patient medical record for this service. | CO-252 |
| N706 | Missing documentation. | CO-252 |
| MA04 | Secondary payment cannot be considered without the identity of or payment information from the primary payer. | Secondary claims |
Fix and resubmit, or appeal?
- Fix and resubmit when the claim itself was wrong: CO-16, CO-4, CO-11, CO-18, CO-22, CO-109. Send a corrected claim (frequency code 7 with the original claim number) when the payer processed the original, or a new claim when it rejected it outright.
- Send records when the payer asked for them: CO-252.
- Appeal when the claim was right and the payer disagrees: CO-50, CO-151, and CO-197 when you had an authorization or an emergency. See how to appeal a behavioral health denial.
- Bill the patient only for PR-group amounts, and for non-covered services only when the patient agreed in advance where the payer requires it.
For the bigger picture, see the top reasons behavioral health claims deny and denial management for behavioral health.
Code wording from the X12 Claim Adjustment Reason Code and Remittance Advice Remark Code lists, read October 19, 2026. X12 updates the lists several times a year, and each payer decides which codes it sends for which problem, so read the remark codes on your own remittance.
Frequently asked questions
What does CO mean on a denial?
CO is the Contractual Obligation group code. The provider is responsible for the adjusted amount and can't bill the patient for it.
What is the difference between CO and PR denial codes?
The reason code can be the same; the group code changes who owes it. CO means the provider absorbs the amount under its contract. PR means the patient owes it under their plan, such as a deductible, coinsurance, or a non-covered service.
What are the most common behavioral health denial codes?
CO-16 (missing information), CO-197 (no authorization), CO-96 and PR-96 (non-covered), CO-50 (medical necessity), CO-252 (documentation required), CO-4 and CO-11 (modifier or diagnosis mismatch), CO-29 (timely filing), and CO-22 or CO-109 (wrong payer).
What is a RARC?
A Remittance Advice Remark Code. It accompanies a CARC and gives the specific problem, for example N290 for a missing rendering provider NPI or M127 for a missing medical record.
Denials worked the day they arrive.
Stable reads every remittance, sorts denials by cause, fixes and resubmits what it can, and drafts appeals for the rest.
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