Overview

  • CARCs are standardized codes on EOBs or ERAs explaining why a claim was paid differently or denied.
  • Maintained by the National Code Maintenance Committee (CMS & WPC).
  • Categories:CO – Contractual Obligations
    • PR – Patient Responsibility
    • OA – Other Adjustments
    • PI – Payer-Initiated Adjustments

Common CARCs & Resolution Tips

  • CO4: Modifier inconsistent or missing → Review CPT/modifier, correct, and resubmit.
  • CO5: Procedure code inconsistent with place of service → Verify location and CPT match.
  • CO16: Missing information → Contact payer for details; send only requested documents.
  • Duplicate Claim: Verify if paid; reconcile or appeal if denial was in error.
  • CO22: May be covered by another payer → Check COB; bill correct insurance.
  • CO27 / CO29: Expenses before/after coverage → Verify coverage dates; update info.
  • CO29 (Timely Filing): Time limit expired → Verify filing deadline; document all submissions.
  • CO45 / CO50: Non-covered or not medically necessary → Review LCD/payer policy; appeal if justified.
  • CO62: Missing/invalid authorization → Verify pre-cert; attach or appeal if error.
  • CO97: Bundled service → Check CCI edits; add proper modifier or appeal.
  • CO109: Not covered by this payer → Verify eligibility; resubmit to correct payer.
  • CO151 / CO152: Frequency or benefit limit reached → Verify timeframe; adjust or appeal.
  • CO206–208: NPI/taxonomy issue → Confirm provider setup; correct and resubmit.
  • CO57: Documentation doesn’t support service → Review notes; correct or appeal.
  • CO55: Experimental/investigational → Check policy; appeal with supporting medical evidence.

Important Tip: Maintain an up-to-date CARC (Claim Adjustment Reason Code) reference list and monitor payer-specific denial patterns to proactively identify and address recurring issues. Create a process to review denial codes, categorize them by payer, and analyze trends to uncover root causes. This approach enables the organization to take focused corrective measures, boost claim accuracy, and minimize recurring denials, leading to improved revenue cycle outcomes and greater operational efficiency.

Dr. Abha Sharma, CPC, COC, CIC, AHIMA approved ICD-10 CM/PCS Trainer, Senior Vice President of Medical Coding and Client Services at Medikigai, brings years of expertise in guiding providers through the maze of payer rules. What started as a passion for helping fellow clinicians, quickly grew into a career focused on turning complex regulations into clear, actionable strategies. From clinical documentation improvement to billing for emerging healthcare technologies, her mission is simple: make coding and insurance rules understandable and practical, so providers can focus on care while practices optimize revenue.

Our specialists can help you decode CARCs, minimize denials, and streamline your claim management process.

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