Denial code · CARC 11
CARC 11 (CO-11): diagnosis and procedure mismatch on BH claims
What CO-11 means, the behavioral-health pairings that trigger it (ABA, TMS, SUD program codes), how diagnosis pointers cause it, and when to correct rather than appeal.
By the ClaimParrot editorial team · Who we are · Reviewed · 4 min read · 5 cited sources
Quick answer
CARC 11 means the payer's edit found that the diagnosis on the line does not support the procedure billed. In behavioral health it shows up when ABA codes carry a non-autism diagnosis, TMS lines carry a diagnosis outside the coverage policy, or a line's diagnosis pointer selects the wrong code. Fix coding errors with a corrected claim; appeal only when the coding was right.
| Item | Detail |
|---|---|
| Code | CARC 11 · Active on the X12 list; checked October 14, 2026 |
| Plain meaning | The payer's edit found that the diagnosis on the line does not go with the procedure code billed, so the line fails as coded. |
| Group codes seen | CO (contractual obligation), OA (other adjustment) |
| Common remark codes | M76, N569, N115 |
| Where it shows up in BH | ABA therapy, TMS, Intensive outpatient (IOP), Psychiatry and medication management |
| Usual next step | Corrected claim if the coding was wrong; appeal if it was right |
| Related codes | CARC 167, CARC 50, CARC 4 |
What does CARC 11 mean?
CARC 11 is a coding-logic denial: the payer compared the diagnosis and procedure codes on the line and decided they do not belong together under its policy. Often the right diagnosis is on the claim but the line points to a different one, which a corrected claim fixes in minutes.
When both codes are right and the payer's policy is the obstacle, the case moves toward CARC 167 (diagnosis not covered) or CARC 50 (not medically necessary), and the answer becomes the policy and the record.
What do CO-11 and OA-11 mean for who pays?
CO-11 is the usual form: coding accuracy is the provider's responsibility, so the line stays unpaid until corrected or overturned, and the patient is not billed. Read an OA-11 together with its remark code. A PR-11 would be unusual and is worth querying before any patient statement goes out.
| Group + reason | What it signals | Who usually carries the balance |
|---|---|---|
| CO-11 | Diagnosis and procedure fail the payer's coding edit | Provider, until corrected or overturned |
| OA-11 | Payer did not classify the adjustment as CO or PR | Read the remark code before posting |
Which remark codes come with CARC 11?
These remark codes tell you whether the diagnosis is missing, invalid or simply not accepted for this procedure.
| Remark code | What it adds | What to check |
|---|---|---|
| M76 | A diagnosis or condition code is missing, incomplete or not valid. | The diagnosis codes and each line's pointer |
| N569 | Not covered when performed for the diagnosis reported. | The payer policy's list of supporting diagnoses |
| N115 | The decision rests on a Local Coverage Determination (LCD), the Medicare contractor's coverage policy. | The LCD billing article's covered ICD-10 codes |
Where does CARC 11 show up in behavioral health?
Behavioral-health CO-11 denials follow benefits that are tied to specific diagnoses. ABA benefits are commonly built around autism spectrum disorder, TMS coverage policies list supporting depression diagnoses, and substance-use program codes expect a substance-use diagnosis. Diagnosis-pointer errors on multi-line claims cause much of the rest.
| Care setting | Typical trigger | Check first |
|---|---|---|
| ABA therapy | ABA codes billed with a diagnosis other than the autism codes the plan requires | The diagnostic evaluation and the codes on the claim |
| TMS | TMS billed with a diagnosis outside the payer policy or LCD | The policy's supporting diagnoses and the record |
| Intensive outpatient (IOP) | Substance-use program code billed with only a mental-health diagnosis | Primary and secondary diagnoses on the claim |
| Psychiatry and medication management | Line points to a Z-code or secondary diagnosis instead of the treated condition | Diagnosis pointers on each line |
Corrected claim, reconsideration or appeal: which fits CARC 11?
Check the coding first. If the line pointed to the wrong diagnosis, or a documented diagnosis was never coded, send a corrected claim. If the diagnosis and procedure were both right, ask for a reconsideration or appeal with the payer's policy, the diagnostic evaluation and the treating clinician's rationale.
- 01Compare the diagnosis codes and line pointers with the clinical documentation for the date of service.
- 02Coding error: correct the diagnosis or pointer and resubmit.
- 03Coding right but still rejected: get the payer's policy, then appeal with the diagnostic evaluation and the policy language that supports coverage.
What evidence resolves a CARC 11?
The evidence is the documented diagnosis and the policy that links it to the service. A diagnostic evaluation by a qualified clinician, dated before or during the service, matters most. For ABA and TMS, payers look for the specific assessment and treatment history their policies name.
- The diagnostic evaluation and who performed it
- The payer policy or LCD listing supporting diagnoses
- Claim lines showing diagnosis pointers
- A treatment plan linking the diagnosis to the service
- For TMS, medication-trial history; for ABA, the autism evaluation
How do Medicare, Medicaid and commercial plans differ on CARC 11?
Medicare contractors publish supporting diagnoses in coverage policies and billing articles; Medicaid programs and MCOs set diagnosis rules service by service; commercial plans write them into medical policies and benefit definitions. The same diagnosis can pass one payer's edit and fail another's.
| Program | What differs |
|---|---|
| Medicare (Original) | LCD billing articles list the ICD-10 codes that support coverage (the TMS LCD, L37086, is one example); remark code N115 points to them. |
| Medicaid | State and MCO billing rules set which diagnoses support each behavioral-health service; check the manual for the service. |
| Commercial and ERISA plans | Medical policies define supporting diagnoses; Aetna's ABA guide, for example, is built around a DSM-5 autism spectrum diagnosis. |
CO-11 on ABA lines after a diagnosis update
A fictional ABA agency's claims for one child came back CO-11. The record carried an autism diagnosis, but an intake update had added an ADHD code as the first diagnosis, and every line pointed to it.
The biller re-pointed the lines to the autism code documented in the diagnostic evaluation, sent corrected claims, and added a pointer check to charge review.
Names, dates, payers and amounts are invented for illustration.
What a ClaimParrot packet does here
- When CARC 11 needs an appeal rather than a corrected claim, an appeal packet answers the payer's stated reason.
- A person checks every packet: $29, or $99 for level of care, and the first is free (pricing).
- No remittances, records or PHI are sent: just the reason and a de-identified summary (Trust & security).
Every draft is reviewed and approved by your team. ClaimParrot does not make medical-necessity determinations or give legal advice.
Frequently asked questions
Is CO-11 a medical-necessity denial?
No. It says the diagnosis and procedure on the line do not fit the payer's coding rules. If the coding is right and the payer still refuses, the dispute can turn into a coverage or medical-necessity question.
Can a diagnosis pointer error cause CO-11?
Yes, and it is among the easiest to fix. If a line points to a secondary diagnosis or a Z-code instead of the treated condition, the edit sees the wrong pairing. Re-point the line and resubmit.
Can we add a diagnosis after a CO-11 to get paid?
Only if the clinician documented that diagnosis for the date of service. Adding an undocumented diagnosis to pass an edit is a compliance risk, not a fix.
How is CARC 11 different from CARC 167?
11 says the diagnosis does not go with this procedure. 167 says the plan does not cover the diagnosis itself, whatever procedure is billed.
Primary sources and references
- Claim Adjustment Reason Codes (CARC) code list · X12 · checked
- Remittance Advice Remark Codes (RARC) code list · X12 · checked
- LCD L37086, Transcranial Magnetic Stimulation (TMS) · CMS Medicare Coverage Database · checked
- Aetna applied behavior analysis medical necessity guide · Aetna · checked
- Aetna provider disputes and appeals overview · Aetna · checked
General information, not legal or medical advice. Payer rules change; confirm deadlines and requirements in the notice and the plan documents. Read our editorial policy.
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