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 |
|---|---|---|
| H27 | The prescribing provider's NPI is either invalid or is not registered. Call Provider … | Details → |
| H28 | The prescribing provider's NPI is invalid (format error). Please correct and resubmi… | Details → |
| H29 | In the future please bill using the NPI of the individual not the organization. | Details → |
| H30 | We are unable to determine the prescribing provider with the NPI provided. Call Provi… | Details → |
| H31 | ICN (Internal Control Number) submitted on request for electronic adjustment is not f… | Details → |
| H32 | Claim number submitted on request for electronic adjustment does not match the claim … | Details → |
| H33 | Rendering provider submitted on request for electronic adjustment does not match the … | Details → |
| H34 | ICN (Internal Control Number) submitted on request for electronic adjustment is alrea… | Details → |
| H35 | ICN (Internal Control Number) submitted for electronic adjustment has already been ad… | Details → |
| H36 | ICN (Internal Control Number) submitted for electronic adjustment previously processe… | Details → |
| H37 | ICN (Internal Control Number) submitted on request for electronic adjustment allowed … | Details → |
| H38 | Electronic adjustment transaction submitted is missing required payer claim control n… | Details → |
| H39 | ICN (Internal Control Number) submitted for electronic adjustment void is for denial … | Details → |
| H40 | DENIED. REBILL WITH THE DATE OF SERVICE AIDS WERE DISPENSED BACK TO THE INJURED WORKE… | Details → |
| I01 | Denied. Required form not received. Direct interpreter services must be documented as… | Details → |
| I02 | Denied. Per the signed "interpreter attestation sheet", interpreter is an employee of… | Details → |
| I03 | Denied. Mileage documentation not received. Printout from software mileage program & … | Details → |
| I04 | Denied. Interpreter services appointment record (ISAR) not received and/or signed by … | Details → |
| I05 | Denied. Mileage billed was not substantiated by appointment record. | Details → |
| I06 | Payment reduced to the maximum allowable minutes per day. Per L&I Payment Policy, lim… | Details → |
| I07 | Denied. Limited to 480 units (8 hours per day), per Interpreter, covers all claims. S… | Details → |
| I10 | This bill was paid a hospital specific POAC for critical access hospital, sub-acute s… | Details → |
| I26 | Travel expense denied. Provider was not in the L&I network on the service date. | Details → |
| I27 | Travel expense denied. Provider did not have an active L&I account on the service dat… | Details → |
| I30 | Denied. No ISAR received or ISAR received does not match billing. | Details → |
| I31 | Denied. The Interpreter Services Appointment Record (ISAR) received for services is m… | Details → |
| I32 | Denied. Total billable mileage submitted or Interpreter Service Appointment record (I… | Details → |
| I33 | Denied. Interpreter Provider number submitted on Interpreter Service Appointment reco… | Details → |
| I34 | Denied. Total Billable minutes submitted on Interpreter Service Appointment record (I… | Details → |
| I35 | Denied. Group services indicator on Interpreter Service Appointment Record (ISAR) doe… | Details → |
| I36 | Denied. Claim number submitted on Interpreter Service Appointment Records for Process… | Details → |
| I37 | Denied. Interpreter Appointment Date of Service on or after 09/01/2015 requires L&I I… | Details → |
| 4 | HCPCS code is inconsistent with modifier used or a required modifier is missing Item… | Details → |
| M01 | Mod 22 was removed to permit auto pricing of daily maximum therapy fee. Refer to fee … | Details → |
| M02 | Denied. Hearing aid repair/modify visit (V5014) must be billed same date w/ repair fe… | Details → |
| M03 | Denied. Restocking fee (5091V) is not payable until refund received from hearing aid … | Details → |
| M04 | Denied. T1017 must be billed with E/M. | Details → |
| M05 | Denied. Procedure 97546 must be billed with 97545. | Details → |
| M06 | Denied. Serial number on repair invoice does not match serial number on warranty. | Details → |
| M07 | Denied. Date of service is after injured worker's date of death. | Details → |
| M08 | Denied. Claim not allowed. Please rebill this service if claim is allowed. | Details → |
| M09 | Bill processed to pay as timely. Originally paid by Medicare but has been determined … | Details → |
| M1 | X-ray not taken within the past 12 months or near enough to the start of treatment. | Details → |
| M10 | Equipment purchases are limited to the first or the tenth month of medical necessity. | Details → |
| M10 | Denied. Bill includes both ICD-9 and ICD-10 codes. Please correct and rebill. | Details → |
| M10 | Equipment purchases are limited to the first or the tenth month of medical necessity. | Details → |
| M100 | We do not pay for an oral anti-emetic drug that is not administered for use immediate… | Details → |
| M100 | We do not pay for an oral anti-emetic drug that is not administered for use immediate… | Details → |
| M101 | Begin to report a G1-G5 modifier with this HCPCS. We will soon begin to deny payment … | Details → |
| M101 | Begin to report a G1-G5 modifier with this HCPCS. We will soon begin to deny payment … | Details → |
| M102 | Service not performed on equipment approved by the FDA for this purpose. | Details → |
| M102 | Service not performed on equipment approved by the FDA for this purpose. | Details → |
| M103 | Information supplied supports a break in therapy. However, the medical information we… | Details → |
| M103 | Information supplied supports a break in therapy. However, the medical information we… | Details → |
| M104 | Information supplied supports a break in therapy. A new capped rental period will beg… | Details → |
| M104 | Information supplied supports a break in therapy. A new capped rental period will beg… | Details → |
| M105 | Information supplied does not support a break in therapy. The medical information we … | Details → |
| M105 | Information supplied does not support a break in therapy. The medical information we … | Details → |
| M106 | Information supplied does not support a break in therapy. A new capped rental period … | Details → |
| M106 | Information supplied does not support a break in therapy. A new capped rental period … | 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.