CARC codes (Claim Adjustment Reason Codes)

Claim Adjustment Reason Codes (CARCs) explain why a claim or service line was paid differently than billed. They appear in the CAS segment of the 835, always paired with a group code. CARCs are maintained by X12 and the list is updated periodically. This page covers the working set you will encounter most; it is not the complete list. The authoritative source is x12.org/codes/claim-adjustment-reason-codes — check it for codes not listed here and for current definitions.

Read the pair, not the code

A CARC alone is incomplete. Group code + CARC is the actionable unit:

CO-45, contractual write-off. Normal.
PR-45, would mean the patient owes the fee-schedule difference. Almost never correct; investigate.
CO-197, you failed to get authorization. Cannot bill the patient.
PR-197, the patient failed to obtain a required authorization. Rare, and depends on the plan.

Always read both. See Group codes.

Patient responsibility

CARC	Meaning	Typical group	Action
1	Deductible amount	PR	Bill the patient
2	Coinsurance amount	PR	Bill the patient
3	Copayment amount	PR	Bill the patient
66	Blood deductible	PR	Bill the patient
142	Monthly Medicaid patient liability	PR	Bill per program rules

Contractual adjustments

CARC	Meaning	Typical group	Action
45	Charge exceeds fee schedule / maximum allowable or contracted arrangement	CO	Write off. The most common adjustment in healthcare. Not a denial.
59	Processed based on multiple or concurrent procedure rules	CO	Verify against contract; often correct
94	Processed in excess of charges	CO/OA	Review, usually a posting or submission issue
131	Claim-specific negotiated discount	CO	Verify against contract
253	Sequestration, federal payment reduction	CO	Medicare; write off

Missing or invalid information

CARC	Meaning	Typical group	Action
16	Claim/service lacks information or has submission/billing error	CO	Read the RARC, CARC 16 alone is a scavenger hunt. The RARC identifies what’s missing.
4	Procedure code inconsistent with the modifier, or a required modifier is missing	CO	Correct the modifier and resubmit
8	Procedure inconsistent with the provider type or specialty	CO	Usually a taxonomy mismatch or a credentialing issue
11	Diagnosis inconsistent with the procedure	CO	Review coding; correct or appeal with documentation
12	Diagnosis inconsistent with the provider type	CO	Review; may be a taxonomy issue
125	Submission/billing error	CO	Read the RARC
206	NPI missing or invalid	CO	Enrollment or claim data problem
288	Referral absent	CO	Obtain and resubmit

Eligibility

CARC	Meaning	Typical group	Action
26	Expenses incurred prior to coverage	CO/PR	Verify coverage dates; may be patient responsibility
27	Expenses incurred after coverage terminated	CO/PR	Verify; rebill correct payer or bill the patient
31	Patient cannot be identified as our insured	CO	Verify member ID and demographics; often a data error
32	Our records indicate the patient is not an eligible dependent	CO	Verify relationship and coverage
33	Insured has no dependent coverage	CO	Verify plan
177	Patient has not met the required eligibility requirements	CO	Verify

Authorization

CARC	Meaning	Typical group	Action
197	Precertification / authorization / notification / pre-treatment absent	CO	Cannot bill the patient. Corrected claim with the auth number, retro-auth, or appeal.
198	Precertification / authorization exceeded	CO	Units or visits beyond what was authorized
15	The authorization number is missing, invalid, or does not apply	CO	Verify the auth matches the service billed
39	Services denied at the time authorization was requested	CO	Appeal on medical necessity

Medical necessity and coverage

CARC	Meaning	Typical group	Action
50	Not deemed a medical necessity by the payer	CO	Appeal with documentation and the applicable coverage policy
96	Non-covered charge(s)	CO/PR	Read the RARC. Benefit design, not an error. May be patient responsibility with proper notice.
97	The benefit for this service is included in the allowance for another service already adjudicated	CO	Bundling. Verify NCCI edits; modifier if clinically justified.
151	Payer determines the information submitted does not support this many services	CO	Documentation or units issue
167	Diagnosis is not covered	CO	Verify coverage policy
204	Service not covered under the patient’s current benefit plan	PR/CO	Benefit design

Coordination of benefits

CARC	Meaning	Typical group	Action
22	This care may be covered by another payer per coordination of benefits	CO/OA	Determine payer order; bill the primary
23	The impact of prior payer(s) adjudication including payments and/or adjustments	OA	Informational on secondary claims
24	Charges are covered under a capitation agreement or managed care plan	CO	Verify arrangement

Timely filing and duplicates

CARC	Meaning	Typical group	Action
29	The time limit for filing has expired	CO	Appeal with clearinghouse acceptance report proving timely submission
18	Exact duplicate claim/service	CO	You resubmitted instead of correcting. Use frequency code 7.

Provider and enrollment

CARC	Meaning	Typical group	Action
185	The rendering provider is not eligible to perform the service billed	CO	Credentialing or scope issue
170	Payment denied when performed by this type of provider	CO	Taxonomy or provider type
171	Payment denied when performed in this type of facility	CO	Place of service
109	Claim not covered by this payer/contractor, send to the correct entity	CO/OA	Rebill the correct payer or MAC
B7	This provider was not certified/eligible to be paid for this procedure on this date	CO	Effective date problem, very common for new hires

Adjustments and recoveries

CARC	Meaning	Typical group	Action
252	An attachment/other documentation is required	CO	Submit the documentation
100	Payment made to patient/insured/responsible party	OA	Recover from the patient
226	Information requested from the billing/rendering provider was not provided	CO	Respond and resubmit
227	Information requested from the patient was not provided	PR/CO	Patient must respond to the payer

The ones that aren’t problems

Worth training billers on explicitly, because they generate wasted work:

CARC	Why it’s not an error
CO-45	The standard contractual write-off. The system worked.
PR-1, PR-2, PR-3	Normal patient cost-sharing. Bill the patient.
CO-253	Medicare sequestration, a statutory reduction.
CO-97	Bundling. Often correct, per NCCI.
CO-96 / CO-204	Benefit design. The service isn’t covered; that isn’t a claim defect.

CPT/coding note

CPT is maintained and licensed by the AMA. This page describes CARCs, which are X12-maintained, and references CPT codes only illustratively. Do not reproduce licensed code sets wholesale. See Code sets overview.

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CARC codes (Claim Adjustment Reason Codes)

Read the pair, not the code

Patient responsibility

Contractual adjustments

Missing or invalid information

Eligibility

Authorization

Medical necessity and coverage

Coordination of benefits

Timely filing and duplicates

Provider and enrollment

Adjustments and recoveries

The ones that aren’t problems

CPT/coding note

​Read the pair, not the code

​Patient responsibility

​Contractual adjustments

​Missing or invalid information

​Eligibility

​Authorization

​Medical necessity and coverage

​Coordination of benefits

​Timely filing and duplicates

​Provider and enrollment

​Adjustments and recoveries

​The ones that aren’t problems

​CPT/coding note

Read the pair, not the code

Patient responsibility

Contractual adjustments

Missing or invalid information

Eligibility

Authorization

Medical necessity and coverage

Coordination of benefits

Timely filing and duplicates

Provider and enrollment

Adjustments and recoveries

The ones that aren’t problems

CPT/coding note