Denial code library
Behavioral-health denial codes, decoded
Plain-English meanings of the claim adjustment reason codes that show up on behavioral-health remittances, with the usual trigger by care setting, the remark codes that travel with them and the next step.
16 reason codes · checked against the X12 lists on
Quick answer
Every adjustment on a remittance carries a group code (who pays), a claim adjustment reason code or CARC (why), and often a remark code or RARC (more detail). Read them together: CO-50 with N115 is a provider-liable medical-necessity denial based on a Medicare coverage policy. This library explains the 16 CARCs behavioral-health teams see most.
What is the difference between a CARC, a RARC and a group code?
The group code says who carries the adjusted amount, the CARC says why the payer adjusted it, and the RARC adds detail the reason code cannot carry. X12 maintains the group and reason codes; CMS maintains the remark codes, which any payer may use.
| Code type | Maintained by | What it tells you | Example |
|---|---|---|---|
| Group code | X12 | Who carries the adjusted amount: provider (CO), patient (PR), payer reduction (PI) or other (OA) | CO |
| Claim adjustment reason code (CARC) | X12 committee; updated three times a year | Why the payer paid less than billed, in one code per adjustment amount | 50 |
| Remittance advice remark code (RARC) | CMS; any payer may use them | Extra detail on the reason, or an alert such as appeal rights | N115 |
Which group code means the patient owes the balance?
Only PR, patient responsibility, signals an amount the patient can be billed, and even then plan terms, your contract and notice rules apply. CO means the provider writes it off, PI is a payer-initiated reduction, and OA means read the reason and remark codes before doing anything.
| Group code | Name | What it signals | Who usually pays |
|---|---|---|---|
| CO | Contractual obligation | A contract between payer and provider, or a regulation, required the adjustment. | The provider writes it off and generally may not bill the patient for it. |
| PR | Patient responsibility | The adjusted amount is something the patient or member can be billed for, such as a deductible, copay or a non-covered service the patient agreed to pay. | The patient, within the plan terms, your contract and any notice rules (for Medicare non-coverage, a valid advance notice). |
| OA | Other adjustment | The payer used this because neither CO nor PR fit; the reason and remark codes carry the real meaning. | Not set by the group code: read the reason and remark codes before posting or billing anyone. |
| PI | Payer-initiated reduction | The payer reduced the amount on its own initiative rather than under a contract term. Medicare does not use PI. | Usually not billable to the patient; dispute it with the payer if no contract term supports it. |
How do you read a denial line on a remittance?
Read the line left to right: the group code, then the reason code and amount, then any remark codes and the policy reference. Decide the route only after all three agree: a billing fix goes back as a corrected claim, a judgment call goes to reconsideration or appeal.
- 01Find the adjustment: group code, reason code and amount, for example CO-197 for the full line charge.
- 02Read the remark codes on the line (and on the claim) and any policy or coverage reference the payer included.
- 03Open the code page here for the behavioral-health causes, then check the record and the authorization before choosing a route.
16 reason codes behavioral-health teams see most
Each page gives the meaning in plain English, what each group code means for who pays, the remark codes that travel with it, the usual trigger by care setting, the next step, the evidence and dated primary sources.
Medical necessity and frequency
The payer questioned whether the care, or this much of it, was needed. Usually answered with records and an appeal.
- CARC 50
Payer judged the service not medically necessary
The payer reviewed the service against its criteria, decided it was not medically necessary, and treated the charge as non-covered.
Usual next step: Appeal (or the payer's clinical reconsideration), with records and criteria
- CARC 151
Payer says the record doesn't support this many services
The payer accepted the type of service but decided the information sent does not justify the number of units or how often it was billed, so it paid fewer or none.
Usual next step: Fix unit errors; appeal frequency judgments with records
Authorization
Approval was missing, exceeded or refused before the service. Start with the authorization record.
- CARC 15Retired 2018
Retired code for an authorization-number problem
A retired X12 code (stopped May 1, 2018) that flagged an authorization number that was absent, wrong, or tied to a different service or provider.
Usual next step: Corrected claim with the right authorization number
- CARC 39
Payer had already refused the approval request
Someone asked the plan for prior approval, the plan said no, and the claim for that same service is denied because of that earlier decision.
Usual next step: Appeal the original authorization decision
- CARC 197
No approval or required notice on file
The plan required precertification, authorization or notification before this service, and it found none it could match to the claim.
Usual next step: Find the approval: corrected claim if it exists, appeal if it does not
- CARC 198
Billed more than the approval covered
An approval existed, but the claim goes past it: more units, days or sessions than approved, or dates outside the approved window.
Usual next step: Reconcile the approval; rebill if an extension exists, appeal the cut if not
Coverage and benefit limits
The plan says the service, the diagnosis or the number of visits falls outside the benefit.
- CARC 96
Charge falls outside the plan's benefits
The plan treats the charge as not covered, and X12 requires a remark code with 96 to say why.
Usual next step: Let the remark code decide: correct, appeal on plan language, or bill per PR rules
- CARC 119
The benefit limit for the period is used up
The plan's limit on this benefit, such as visits or days per year or a lifetime maximum, has been reached, so the payer stops paying for more.
Usual next step: Verify the count; then request an exception or appeal the limit
- CARC 167
Plan does not cover the diagnosis billed
The plan excludes or does not cover the diagnosis on the claim, so services billed for it are refused whatever the procedure.
Usual next step: Correct if miscoded; otherwise appeal with plan language
Coding and claim data
A modifier, diagnosis, bundling edit or missing field stopped the line. Usually fixed with a corrected claim.
- CARC 4
Modifier does not fit the billed procedure
The modifier on the line is wrong, missing where required, or does not belong with that procedure code, so the payer will not accept the line as billed.
Usual next step: Corrected claim with the right modifier
- CARC 11
Diagnosis does not support the billed procedure
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.
Usual next step: Corrected claim if the coding was wrong; appeal if it was right
- CARC 16
Claim is missing data or has a billing error
Something on the claim is missing, invalid or entered wrong. The remark code that must accompany 16 names the field to fix.
Usual next step: Corrected claim (not an appeal)
- CARC 97
Paid as part of another service, not separately
The payer considers this service part of another service it has already processed, so it pays nothing extra for it.
Usual next step: Write off, or correct with a modifier if the services were truly distinct
Provider eligibility
The payer will not pay this provider type, or this clinician, for the service billed.
- CARC 170
Payer won't pay this service from this provider type
The payer does not pay for this service when the type of provider on the claim, such as a counselor, an associate or a peer specialist, performs or bills it.
Usual next step: Correct the billing provider if allowed; otherwise appeal with license and plan rules
- CARC 185
Rendering clinician isn't eligible for this service
The clinician listed as rendering provider was not eligible, enrolled or credentialed with the payer for this service on the date it was performed.
Usual next step: Fix enrollment or data, then rebill; appeal only if the clinician was eligible
Filing limits
The claim arrived after the payer's filing window. Proof of timely submission is the whole case.
- CARC 29
Claim reached the payer after its filing deadline
The payer received the claim after its filing window closed, so it will not pay unless you prove timely submission or an exception applies.
Usual next step: Reconsideration with proof of timely filing
Have a whole remittance line?
Type it into the lookup, for example CO-197 M62 or PR-96 N130. It explains each code and runs entirely in your browser; no patient details needed.
Frequently asked questions
Why do some remittances show the same reason code with different group codes?
Because the reason and the liability are separate questions. CARC 50 says the payer found the service not medically necessary; CO or PR in front of it says whether the provider or the patient carries that amount under the contract, notice rules and plan terms.
Are these the official X12 descriptions?
No. Each page explains the code in our own words and links the X12 list for the official text. Use the X12 list when you need the exact wording, for example in a contract dispute.
How current is the denial code library?
We checked every code against the X12 lists on October 14, 2026. CMS says the code lists are updated three times a year, around March, July and November, and we re-check after each update.
My remittance shows a code that is not in this library. What now?
Look it up on the X12 list and read the remark code with it. The denial code lookup tells you when a code is outside our behavioral-health library and links the right X12 list.
Primary sources and references
- Claim Adjustment Reason Codes (CARC) code list · X12 · checked
- Remittance Advice Remark Codes (RARC) code list · X12 · checked
- Claim Adjustment Group Codes code list · X12 · checked
- Medicare Claims Processing Manual, Chapter 22, §60: group, reason and remark codes on the remittance advice · CMS · checked
- CMS Change Request 14293 (Transmittal 13481): CORE 360 uniform use of CARCs, RARCs and group codes · CMS · checked
Code meanings are written in our own words; the X12 lists hold the official descriptions. General information, not legal or billing advice: the remittance, the denial notice, your contract and the plan documents control. Read our editorial policy.
Decode the line.Then decide the route.