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 |
|---|---|---|
| N505 | Alert: This response includes only services that could be estimated in real-time. No … | Details → |
| N506 | Alert: This is an estimate of the member's liability based on the information availab… | Details → |
| N506 | Alert: This is an estimate of the member's liability based on the information availab… | Details → |
| N507 | Plan distance requirements have not been met. | Details → |
| N507 | Plan distance requirements have not been met. | Details → |
| N508 | Alert: This real-time claim adjudication response represents the member responsibilit… | Details → |
| N508 | Alert: This real-time claim adjudication response represents the member responsibilit… | Details → |
| N509 | Alert: A current inquiry shows the member's Consumer Spending Account contains suffic… | Details → |
| N509 | Alert: A current inquiry shows the member's Consumer Spending Account contains suffic… | Details → |
| N51 | Electronic interchange agreement not on file for provider/submitter. | Details → |
| N51 | Electronic interchange agreement not on file for provider/submitter. | Details → |
| N510 | Alert: A current inquiry shows the member's Consumer Spending Account does not contai… | Details → |
| N510 | Alert: A current inquiry shows the member's Consumer Spending Account does not contai… | Details → |
| N511 | Alert: Information on the availability of Consumer Spending Account funds to cover th… | Details → |
| N511 | Alert: Information on the availability of Consumer Spending Account funds to cover th… | Details → |
| N512 | Alert: This is the initial remit of a non-NCPDP claim originally submitted real-time … | Details → |
| N512 | Alert: This is the initial remit of a non-NCPDP claim originally submitted real-time … | Details → |
| N513 | Alert: This is the initial remit of a non-NCPDP claim originally submitted real-time … | Details → |
| N513 | Alert: This is the initial remit of a non-NCPDP claim originally submitted real-time … | Details → |
| N514 | Consult plan benefit documents/guidelines for information about restrictions for this… | Details → |
| N514 | Consult plan benefit documents/guidelines for information about restrictions for this… | Details → |
| N515 | Alert: Submit this claim to the patient's other insurer for potential payment of supp… | Details → |
| N515 | Alert: Submit this claim to the patient's other insurer for potential payment of supp… | Details → |
| N516 | Records indicate a mismatch between the submitted NPI and EIN. | Details → |
| N516 | Records indicate a mismatch between the submitted NPI and EIN. | Details → |
| N517 | Resubmit a new claim with the requested information. | Details → |
| N517 | Resubmit a new claim with the requested information. | Details → |
| N517 | Invalid modifier for date of service | Details → |
| N517 | Precertification/authorization/notification/pre-treatment number may be valid but doe… | Details → |
| N518 | No separate payment for accessories when furnished for use with oxygen equipment. | Details → |
| N518 | No separate payment for accessories when furnished for use with oxygen equipment. | Details → |
| N519 | Invalid combination of HCPCS modifiers. | Details → |
| N519 | HCPCS code is inconsistent with modifier used or required modifier is missing | Details → |
| N519 | Invalid combination of HCPCS modifiers. | Details → |
| N52 | Patient not enrolled in the billing provider's managed care plan on the date of servi… | Details → |
| N52 | Patient not enrolled in the billing provider's managed care plan on the date of servi… | Details → |
| N520 | Alert: Payment made from a Consumer Spending Account. | Details → |
| N520 | Alert: Payment made from a Consumer Spending Account. | Details → |
| N521 | Mismatch between the submitted provider information and the provider information stor… | Details → |
| N521 | Mismatch between the submitted provider information and the provider information stor… | Details → |
| N522 | Duplicate of a claim processed, or to be processed, as a crossover claim. | Details → |
| N522 | Duplicate of a claim processed, or to be processed, as a crossover claim. | Details → |
| N522 | Duplicate claim has already been submitted and processed | Details → |
| N523 | The limitation on outlier payments defined by this payer for this service period has … | Details → |
| N523 | The limitation on outlier payments defined by this payer for this service period has … | Details → |
| N524 | Based on policy this payment constitutes payment in full. | Details → |
| N524 | Based on policy this payment constitutes payment in full. | Details → |
| N525 | These services are not covered when performed within the global period of another ser… | Details → |
| N525 | These services are not covered when performed within the global period of another ser… | Details → |
| N526 | Not qualified for recovery based on employer size. | Details → |
| N526 | Not qualified for recovery based on employer size. | Details → |
| N527 | We processed this claim as the primary payer prior to receiving the recovery demand. | Details → |
| N527 | We processed this claim as the primary payer prior to receiving the recovery demand. | Details → |
| N528 | Patient is entitled to benefits for Institutional Services only. | Details → |
| N528 | Patient is entitled to benefits for Institutional Services only. | Details → |
| N529 | Patient is entitled to benefits for Professional Services only. | Details → |
| N529 | Patient is entitled to benefits for Professional Services only. | Details → |
| N53 | Missing/incomplete/invalid point of pick-up address. | Details → |
| N53 | Missing/incomplete/invalid point of pick-up address. | Details → |
| N530 | Not Qualified for Recovery based on enrollment information. | 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.