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 updated periodically. This page covers common dental-billing scenarios rather than the complete code set. Use x12.org/codes/claim-adjustment-reason-codes for current definitions and codes not listed here.

Interpret the CARC and group code together

A CARC should be read with its group code:

CO-45 generally reports a contractual fee adjustment.
PR-45 reports the fee-schedule difference as patient responsibility and warrants review against the contract and plan.
CO-197 classifies a missing authorization adjustment as the provider’s contractual obligation.
PR-197 classifies it as patient responsibility; confirm the plan facts, contract, and notice rules before billing.

Always read both. See Group codes.

Reading dental remittances: there is no “downgrade code”

Downgrades under an alternate-benefit or LEAT provision, frequency limits, and exhausted annual maximums do not have dedicated CARCs. They use ordinary group and reason codes. A downgraded composite may appear as a paid line whose allowed amount reflects the amalgam alternative, while a frequency-limited or over-maximum service may appear as a noncovered or benefit-design adjustment. Do not classify a dental remittance as a denial, downgrade, or benefit limitation from the CARC alone. Read the group code, allowed amount, contracted fee, plan terms, and any RARC together. Confirm that the payer applied the plan correctly before deciding whether to post, bill the patient, correct the claim, or appeal. See Denials vs downgrades and the denial code playbook.

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
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, including whether a leased-network rate was applied; see Network leasing
253	Sequestration, federal payment reduction	CO	Medicare only; rare in dental; 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 because CARC 16 alone does not identify the missing item.
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; DHMO plans commonly require specialist referrals

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

A predetermination is voluntary, so its absence alone does not trigger these codes. A preauthorization is required before treatment by some plans, mainly Medicaid programs and DHMOs, and the codes below may report a missing 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; watch ortho continuation claims
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 with clinical documentation

Necessity and coverage

CARC	Meaning	Typical group	Action
50	Not deemed a necessity by the payer	CO	Appeal with radiographs, charting, narrative, and the payer’s own coverage criteria
96	Non-covered charge(s)	CO/PR	Read the RARC. Benefit design; cosmetic exclusions, adult ortho, implant exclusions. 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 the payer’s bundling policy; appeal with documentation if the service was genuinely separate.
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; for dependents, the birthday rule; 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	Service location issue
109	Claim not covered by this payer/contractor, send to the correct entity	CO/OA	Rebill the correct payer; often the Medicaid dental benefit administrator rather than the state
B7	This provider was not certified/eligible to be paid for this procedure on this date	CO	Effective date problem; very common for new associates and freshly acquired offices

Adjustments and recoveries

CARC	Meaning	Typical group	Action
252	An attachment/other documentation is required	CO	Submit the documentation; radiographs, perio charting, narrative; through the payer’s channel; see Dental attachments
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

Adjustments that may be expected

Train billers to recognize these adjustments so they do not enter an appeal queue automatically:

CARC	Why it may be expected
CO-45	The standard contractual write-off and, in dental, commonly the PPO write-off line. Verify it against the fee schedule.
PR-1, PR-2, PR-3	Normal patient cost-sharing. Bill the patient.
CO-97	Bundling, per the payer’s policy. Often correct.
CO-96 / CO-204	Benefit design. The service isn’t covered; that isn’t a claim defect.
Downgrades and limitations	Alternate-benefit pricing, frequency limits, and exhausted maximums arrive on ordinary codes. If the payer applied the plan correctly, route the amount according to the group code rather than appealing automatically.

Coding note

CARCs are X12-maintained. CDT is maintained and licensed by the ADA (and CPT by the AMA); this page references procedure-code concepts only illustratively. Do not reproduce licensed code sets wholesale. See Code sets overview.

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CARC codes (Claim Adjustment Reason Codes)

Interpret the CARC and group code together

Reading dental remittances: there is no “downgrade code”

Patient responsibility

Contractual adjustments

Missing or invalid information

Eligibility

Authorization

Necessity and coverage

Coordination of benefits

Timely filing and duplicates

Provider and enrollment

Adjustments and recoveries

Adjustments that may be expected

Coding note

​Interpret the CARC and group code together

​Reading dental remittances: there is no “downgrade code”

​Patient responsibility

​Contractual adjustments

​Missing or invalid information

​Eligibility

​Authorization

​Necessity and coverage

​Coordination of benefits

​Timely filing and duplicates

​Provider and enrollment

​Adjustments and recoveries

​Adjustments that may be expected

​Coding note

Interpret the CARC and group code together

Reading dental remittances: there is no “downgrade code”

Patient responsibility

Contractual adjustments

Missing or invalid information

Eligibility

Authorization

Necessity and coverage

Coordination of benefits

Timely filing and duplicates

Provider and enrollment

Adjustments and recoveries

Adjustments that may be expected

Coding note