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 |
|---|---|---|
| N32 | Claim must be submitted by the provider who rendered the service. | Details → |
| N32 | Claim must be submitted by the provider who rendered the service. | Details → |
| N320 | Missing/incomplete/invalid Home Health Certification Period. | Details → |
| N320 | Missing/incomplete/invalid Home Health Certification Period. | Details → |
| N321 | Missing/incomplete/invalid last admission period. | Details → |
| N321 | Missing/incomplete/invalid last admission period. | Details → |
| N322 | Missing/incomplete/invalid last certification date. | Details → |
| N322 | Missing/incomplete/invalid last certification date. | Details → |
| N323 | Missing/incomplete/invalid last contact date. | Details → |
| N323 | Missing/incomplete/invalid last contact date. | Details → |
| N324 | Missing/incomplete/invalid last seen/visit date. | Details → |
| N324 | Missing/incomplete/invalid last seen/visit date. | Details → |
| N325 | Missing/incomplete/invalid last worked date. | Details → |
| N325 | Missing/incomplete/invalid last worked date. | Details → |
| N326 | Missing/incomplete/invalid last x-ray date. | Details → |
| N326 | Missing/incomplete/invalid last x-ray date. | Details → |
| N327 | Missing/incomplete/invalid other insured birth date. | Details → |
| N327 | Missing/incomplete/invalid other insured birth date. | Details → |
| N328 | Missing/incomplete/invalid Oxygen Saturation Test date. | Details → |
| N328 | Missing/incomplete/invalid Oxygen Saturation Test date. | Details → |
| N329 | Missing/incomplete/invalid patient birth date. | Details → |
| N329 | Missing/incomplete/invalid patient birth date. | Details → |
| N33 | No record of health check prior to initiation of treatment. | Details → |
| N33 | No record of health check prior to initiation of treatment. | Details → |
| N330 | Missing/incomplete/invalid patient death date. | Details → |
| N330 | Missing/incomplete/invalid patient death date. | Details → |
| N331 | Missing/incomplete/invalid physician order date. | Details → |
| N331 | Missing/incomplete/invalid physician order date. | Details → |
| N332 | Missing/incomplete/invalid prior hospital discharge date. | Details → |
| N332 | Missing/incomplete/invalid prior hospital discharge date. | Details → |
| N333 | Missing/incomplete/invalid prior placement date. | Details → |
| N333 | Missing/incomplete/invalid prior placement date. | Details → |
| N334 | Missing/incomplete/invalid re-evaluation date. | Details → |
| N334 | Missing/incomplete/invalid re-evaluation date. | Details → |
| N335 | Missing/incomplete/invalid referral date. | Details → |
| N335 | Missing/incomplete/invalid referral date. | Details → |
| N336 | Missing/incomplete/invalid replacement date. | Details → |
| N336 | Missing/incomplete/invalid replacement date. | Details → |
| N337 | Missing/incomplete/invalid secondary diagnosis date. | Details → |
| N337 | Missing/incomplete/invalid secondary diagnosis date. | Details → |
| N338 | Missing/incomplete/invalid shipped date. | Details → |
| N338 | Missing/incomplete/invalid shipped date. | Details → |
| N339 | Missing/incomplete/invalid similar illness or symptom date. | Details → |
| N339 | Missing/incomplete/invalid similar illness or symptom date. | Details → |
| N34 | Incorrect claim form/format for this service. | Details → |
| N34 | Incorrect claim form/format for this service. | Details → |
| N340 | Missing/incomplete/invalid subscriber birth date. | Details → |
| N340 | Missing/incomplete/invalid subscriber birth date. | Details → |
| N341 | Missing/incomplete/invalid surgery date. | Details → |
| N341 | Missing/incomplete/invalid surgery date. | Details → |
| N342 | Missing/incomplete/invalid test performed date. | Details → |
| N342 | Missing/incomplete/invalid test performed date. | Details → |
| N343 | Missing/incomplete/invalid Transcutaneous Electrical Nerve Stimulator (TENS) trial st… | Details → |
| N343 | Missing/incomplete/invalid Transcutaneous Electrical Nerve Stimulator (TENS) trial st… | Details → |
| N344 | Missing/incomplete/invalid Transcutaneous Electrical Nerve Stimulator (TENS) trial en… | Details → |
| N344 | Missing/incomplete/invalid Transcutaneous Electrical Nerve Stimulator (TENS) trial en… | Details → |
| N345 | Date range not valid with units submitted. | Details → |
| N345 | Date range not valid with units submitted. | Details → |
| N346 | Missing/incomplete/invalid oral cavity designation code. | Details → |
| N346 | Missing/incomplete/invalid oral cavity designation code. | 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.