Denials & rebilling

Missing/Invalid/Incomplete Claim Information

The payer is saying the claim itself was incomplete or contained an error somewhere — a required field is missing, invalid, or does not match what the payer has on file.

Patient Not Eligible / Cannot Be Identified as Insured

The payer cannot match the patient/member information on the claim to an active member on their system — either the ID is wrong, the patient is not covered by that plan, or an eligibility condition (waiting per…

Coverage Not in Effect on Date of Service (Termination)

The payer's records show the patient's coverage ended before (CO-27) or had not started as of (CO-26) the date of service billed.

Coordination of Benefits (COB) — Another Payer May Be Primary (CO-22)

CARC 22 means the payer believes another plan may be primary for this care, or the claim did not carry the prior payer's information. This is a payer-order and COB-data finding. It is a different finding from CARC 23, which reports the impact of a prior payer's adjudication.

Impact of Prior-Payer Adjudication (OA-23 / narrow Medicare CO-23) & the "Recoupment Denial"

CARC 23 reports the impact of the prior payer's adjudication — payments and adjustments — and X12 defines it for use only with group code OA. On its own it is informational, not a denial, and not a reason to rebill. Some teams call it the "recoupment denial," but a true provider-level takeback appears separately in the 835 provider-level balance (PLB) section. Medicare also has a narrow conditional-payment implementation that uses CO-23 with M32 and N4.

Authorization/Precertification Absent or Exceeded

The payer required prior authorization for this service and either did not receive one at all (CO-197) or the billed service/units/dates exceed what was actually authorized (CO-198).

Referral Absent or Exceeded

The plan (commonly an HMO/managed-care or Medicaid MCO plan requiring PCP referrals) either has no referral on file for this service or the service exceeds what the referral authorized.

Medical Necessity Not Met

The payer's coverage policy (LCD/NCD or commercial medical policy) does not consider this service medically necessary for the diagnosis/circumstances billed.

Noncovered / Statutorily Excluded Service

The service billed simply is not a covered benefit under this patient's plan (or, for Medicare, is excluded by statute) — this is different from a medical-necessity denial, which concerns whether a covered bene…

Bundled / Incidental Procedure (NCCI Cross-reference for Inclusive Procedures)

The payer is not paying separately for this service because it considers it a component of, or incidental to, another procedure already billed and paid on the same claim or encounter — the payment for the small…

Exact Duplicate Claim/Service

The payer's system has already received and processed an identical claim for this patient, date of service, and procedure — this submission is being treated as a repeat, not a new claim.

Timely Filing Limit Expired

The claim was received by the payer after the deadline allowed in the plan/contract (or, for Medicare, after the 12-month statutory limit), so it is being denied for lateness rather than for any clinical or cod…

Diagnosis Inconsistent with Procedure

The diagnosis code billed does not logically or per payer policy support the procedure code billed for this patient (e.g., a diagnosis that does not justify the specific test/procedure performed).

Modifier Issues (Inconsistent or Invalid Modifier)

The modifier appended to the procedure code either doesn't make sense for that code, is not a valid modifier for the date of service, or a required modifier is missing entirely.

Provider Not Certified/Eligible (Enrollment)

The payer's enrollment records show this provider was not enrolled, not credentialed with this specific plan, or not eligible to bill this specific service/specialty combination as of the date of service.

Rendering Provider Not Eligible to Perform Service

The specific individual listed as having performed the service is not, per the payer's records, allowed to perform/bill that type of service — this differs from D14 (overall enrollment) in that it focuses on sc…

NPI Missing, Invalid, or Not Matched

The claim is missing an NPI where one is required, the NPI is not in a valid format, or the NPI submitted does not match the provider name/role on the payer's file (including PECOS ordering/referring records, w…

Place-of-Service Inconsistent or Invalid

The two-digit Place of Service (POS) code on the claim doesn't match the type of service billed, or the payer considers that setting invalid/inappropriate for this specific service.

Frequency Limitation Exceeded

The payer's records show this service (or this many units of it) has already been provided more times, or in greater quantity, than the plan/coverage policy or NCCI MUE allows within the relevant time period.

Benefit Maximum / Lifetime Maximum Reached

The patient's plan only covers a set amount/number of this service per period (CO-119) or ever (CO-35/CO-149), and that limit has already been used up.

Missing Documentation / Attachment Required

The payer cannot finish processing this claim without additional supporting documentation (medical records, operative note, invoice, questionnaire, etc.) that either was never sent, was the wrong document, or w…

Payer Processing — Claim Pending Further Review

The payer has not made a final decision yet — the claim/line is under active review (e.g., medical review, COB investigation, fraud/utilization review) and a corrected determination is expected later.

Patient Responsibility (Deductible/Coinsurance/Copay)

The payer has processed and approved the claim; this specific dollar amount is the patient's contractual share of the cost (deductible, coinsurance, or copay), not a payer denial of the service itself.

Contractual Adjustment / Fee Schedule Write-off

The amount billed was simply higher than the contracted or fee-schedule allowed amount; the difference is a required write-off under the provider's contract with the payer, not something the patient owes (unles…

Patient/Insured ID and Name Mismatch (Registration)

The insurance ID number and the patient/subscriber name submitted on the claim do not match what the payer has on file, so the payer's system cannot locate the correct member record to adjudicate the claim.

Claim Sent to Wrong Payer/Contractor

The claim was submitted to a payer or contractor that does not have jurisdiction or responsibility for this patient, service, or claim type;