Instantly find explanations, causes, and resolution steps for every Claim Adjustment Reason Code (CARC) and Remark Code.
Claim Adjustment Reason Codes (CARC) explain why a payment differs from what was billed. Every 835 ERA and EOB uses these standardized codes.
Search any code or keyword above. Each page includes the full description, common causes, resolution steps, and appeal guidance.
Each denial code page also links to a dedicated Remark Code page — optimized for providers searching for ERA remark code context.
Most denials are reversible. Our guides walk you through the correct steps to correct, resubmit, or formally appeal each denial type.
| Code | Description | View |
|---|---|---|
| M107 | Payment reduced as 90-day rolling average hematocrit for ESRD patient exceeded 36.5%. | Details → |
| M107 | Payment reduced as 90-day rolling average hematocrit for ESRD patient exceeded 36.5%. | Details → |
| M108 | Missing/incomplete/invalid provider identifier for the provider who interpreted the d… | Details → |
| M108 | Missing/incomplete/invalid provider identifier for the provider who interpreted the d… | Details → |
| M109 | We have provided you with a bundled payment for a teleconsultation. You must send 25 … | Details → |
| M109 | We have provided you with a bundled payment for a teleconsultation. You must send 25 … | Details → |
| M11 | DME, orthotics and prosthetics must be billed to the DME carrier who services the pat… | Details → |
| M11 | Denied. 10th-25th diagnosis code is invalid for first date of service. | Details → |
| M11 | DME, orthotics and prosthetics must be billed to the DME carrier who services the pat… | Details → |
| M110 | Missing/incomplete/invalid provider identifier for the provider from whom you purchas… | Details → |
| M110 | Missing/incomplete/invalid provider identifier for the provider from whom you purchas… | Details → |
| M111 | We do not pay for chiropractic manipulative treatment when the patient refuses to hav… | Details → |
| M111 | We do not pay for chiropractic manipulative treatment when the patient refuses to hav… | Details → |
| M112 | Reimbursement for this item is based on the single payment amount required under the … | Details → |
| M112 | Reimbursement for this item is based on the single payment amount required under the … | Details → |
| M113 | Our records indicate that this patient began using this item/service prior to the cur… | Details → |
| M113 | Our records indicate that this patient began using this item/service prior to the cur… | Details → |
| M114 | This service/procedure requires that a qualifying service/procedure be received and c… | Details → |
| M114 | This service was processed in accordance with rules and guidelines under the DMEPOS C… | Details → |
| M114 | This service was processed in accordance with rules and guidelines under the DMEPOS C… | Details → |
| M114 | HCPCS code is inconsistent with modifier used or a required modifier is missing Item… | Details → |
| M114 | Non-covered charge(s). This service was processed in accordance with rules and guide… | Details → |
| M115 | Procedure/service was partially or fully furnished by another provider. This item is… | Details → |
| M115 | This item is denied when provided to this patient by a non-contract or non-demonstrat… | Details → |
| M115 | This item is denied when provided to this patient by a non-contract or non-demonstrat… | Details → |
| M115 | Non-covered charge(s). This service was processed in accordance with rules and guide… | Details → |
| M116 | Processed under a demonstration project or program. Project or program is ending and … | Details → |
| M116 | Processed under a demonstration project or program. Project or program is ending and … | Details → |
| M117 | Not covered unless submitted via electronic claim. | Details → |
| M117 | Not covered unless submitted via electronic claim. | Details → |
| M118 | Letter to follow containing further information. | Details → |
| M118 | Letter to follow containing further information. | Details → |
| M119 | Missing/incomplete/invalid/ deactivated/withdrawn National Drug Code (NDC). | Details → |
| M119 | Missing/incomplete/invalid/ deactivated/withdrawn National Drug Code (NDC). | Details → |
| M12 | Diagnostic tests performed by a physician must indicate whether purchased services ar… | Details → |
| M12 | Denied. 10th-25th diagnosis code is not sufficiently specific. | Details → |
| M12 | Diagnostic tests performed by a physician must indicate whether purchased services ar… | Details → |
| M120 | Missing/incomplete/invalid provider identifier for the substituting physician who fur… | Details → |
| M120 | Missing/incomplete/invalid provider identifier for the substituting physician who fur… | Details → |
| M121 | We pay for this service only when performed with a covered cryosurgical ablation. | Details → |
| M121 | We pay for this service only when performed with a covered cryosurgical ablation. | Details → |
| M122 | Missing/incomplete/invalid level of subluxation. | Details → |
| M122 | Missing/incomplete/invalid level of subluxation. | Details → |
| M123 | Missing/incomplete/invalid name, strength, or dosage of the drug furnished. | Details → |
| M123 | Missing/incomplete/invalid name, strength, or dosage of the drug furnished. | Details → |
| M124 | Missing indication of whether the patient owns the equipment that requires the part o… | Details → |
| M124 | Missing indication of whether the patient owns the equipment that requires the part o… | Details → |
| M124 | Item billed does not have base equipment on file. Main equipment is missing therefore… | Details → |
| M125 | Missing/incomplete/invalid information on the period of time for which the service/su… | Details → |
| M125 | Missing/incomplete/invalid information on the period of time for which the service/su… | Details → |
| M126 | Missing/incomplete/invalid individual lab codes included in the test. | Details → |
| M126 | Missing/incomplete/invalid individual lab codes included in the test. | Details → |
| M127 | Missing patient medical record for this service. | Details → |
| M127 | Missing patient medical record for this service. | Details → |
| M127 | These are non-covered services because this is not deemed a 'medical necessity' by th… | Details → |
| M128 | Missing/incomplete/invalid date of the patient's last physician visit. | Details → |
| M128 | Missing/incomplete/invalid date of the patient's last physician visit. | Details → |
| M129 | Missing/incomplete/invalid indicator of x-ray availability for review. | Details → |
| M129 | Missing/incomplete/invalid indicator of x-ray availability for review. | Details → |
| M13 | Only one initial visit is covered per specialty per medical group. | Details → |
Medical claim denial codes — formally known as Claim Adjustment Reason Codes (CARC) — are standardized identifiers maintained by the X12 standards body and used across all Medicare, Medicaid, and commercial payer 835 electronic remittance transactions. When a claim is paid at a different amount than billed, at least one CARC code must accompany the remittance advice to indicate the specific reason for the adjustment.
The most frequently encountered codes include CO-16 (missing or invalid claim information), CO-45 (charges exceeding fee schedule), PR-1 (patient deductible), CO-29 (timely filing deadline exceeded), and CO-4 (procedure code inconsistent with modifier). Each represents a distinct, actionable reason that has a defined resolution pathway.