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 |
|---|---|---|
| N663 | Adjusted based on an agreed amount. | Details → |
| N664 | Adjusted based on a legal settlement. | Details → |
| N664 | Adjusted based on a legal settlement. | Details → |
| N665 | Services by an unlicensed provider are not reimbursable. | Details → |
| N665 | Services by an unlicensed provider are not reimbursable. | Details → |
| N666 | Only one evaluation and management code at this service level is covered during the c… | Details → |
| N666 | Only one evaluation and management code at this service level is covered during the c… | Details → |
| N667 | Missing prescription. | Details → |
| N667 | Missing prescription. | Details → |
| N668 | Incomplete/invalid prescription. | Details → |
| N668 | Incomplete/invalid prescription. | Details → |
| N668 | An initial Certificate of Medical Necessity (CMN) or DME Information Form (DIF) was n… | Details → |
| N669 | Adjusted based on the Medicare fee schedule. | Details → |
| N669 | Adjusted based on the Medicare fee schedule. | Details → |
| N67 | Professional provider services not paid separately. Included in facility payment unde… | Details → |
| N67 | Professional provider services not paid separately. Included in facility payment unde… | Details → |
| N670 | This service code has been identified as the primary procedure code subject to the Me… | Details → |
| N670 | This service code has been identified as the primary procedure code subject to the Me… | Details → |
| N671 | Payment based on a jurisdiction cost-charge ratio. | Details → |
| N671 | Payment based on a jurisdiction cost-charge ratio. | Details → |
| N672 | Alert: Amount applied to Health Insurance Offset. | Details → |
| N672 | Alert: Amount applied to Health Insurance Offset. | Details → |
| N673 | Reimbursement has been calculated based on an outpatient per diem or an outpatient fa… | Details → |
| N673 | Reimbursement has been calculated based on an outpatient per diem or an outpatient fa… | Details → |
| N674 | This service/procedure requires that a qualifying service/procedure be received and c… | Details → |
| N674 | Not covered unless a pre-requisite procedure/service has been provided. | Details → |
| N674 | Not covered unless a pre-requisite procedure/service has been provided. | Details → |
| N675 | Additional information is required from the injured party. | Details → |
| N675 | Additional information is required from the injured party. | Details → |
| N676 | Service does not qualify for payment under the Outpatient Facility Fee Schedule. | Details → |
| N676 | Service does not qualify for payment under the Outpatient Facility Fee Schedule. | Details → |
| N677 | Alert: Films/Images will not be returned. | Details → |
| N677 | Alert: Films/Images will not be returned. | Details → |
| N678 | Missing post-operative images/visual field results. | Details → |
| N678 | Missing post-operative images/visual field results. | Details → |
| N679 | Incomplete/Invalid post-operative images/visual field results. | Details → |
| N679 | Incomplete/Invalid post-operative images/visual field results. | Details → |
| N68 | Prior payment being cancelled as we were subsequently notified this patient was cover… | Details → |
| N68 | Prior payment being cancelled as we were subsequently notified this patient was cover… | Details → |
| N680 | Missing/Incomplete/Invalid date of previous dental extractions. | Details → |
| N680 | Missing/Incomplete/Invalid date of previous dental extractions. | Details → |
| N681 | Missing/Incomplete/Invalid full arch series. | Details → |
| N681 | Missing/Incomplete/Invalid full arch series. | Details → |
| N682 | Missing/Incomplete/Invalid history of prior periodontal therapy/maintenance. | Details → |
| N682 | Missing/Incomplete/Invalid history of prior periodontal therapy/maintenance. | Details → |
| N683 | Missing/Incomplete/Invalid prior treatment documentation. | Details → |
| N683 | Missing/Incomplete/Invalid prior treatment documentation. | Details → |
| N684 | Payment denied as this is a specialty claim submitted as a general claim. | Details → |
| N684 | Payment denied as this is a specialty claim submitted as a general claim. | Details → |
| N685 | Missing/Incomplete/Invalid Prosthesis, Crown or Inlay Code. | Details → |
| N685 | Missing/Incomplete/Invalid Prosthesis, Crown or Inlay Code. | Details → |
| N686 | Missing/incomplete/Invalid questionnaire needed to complete payment determination. | Details → |
| N686 | Missing/incomplete/Invalid questionnaire needed to complete payment determination. | Details → |
| N687 | Alert: This reversal is due to a retroactive disenrollment. | Details → |
| N687 | Alert: This reversal is due to a retroactive disenrollment. | Details → |
| N688 | Alert: This reversal is due to a medical or utilization review decision. | Details → |
| N688 | Alert: This reversal is due to a medical or utilization review decision. | Details → |
| N689 | Alert: This reversal is due to a retroactive rate change. | Details → |
| N689 | Alert: This reversal is due to a retroactive rate change. | Details → |
| N69 | Alert: PPS (Prospective Payment System) code changed by claims processing system. | 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.