Treatment not deemed medically necessary
Reviewed by
Medical Billing Compliance Team
Healthcare Revenue Cycle Specialists
Last reviewed: February 5, 2026
📋 Official X12 Definition
CARC 58: Treatment not deemed medically necessary. This code is maintained by the X12 organization as part of the External Code List for Claim Adjustment Reason Codes used in electronic healthcare transactions per HIPAA requirements.
💬 What This Means (Plain English)
This code indicates: treatment not deemed medically necessary. This is a standard claim adjustment reason code used to explain why the claim was processed differently than billed.
📖 Detailed Explanation
CARC Code 58 (Treatment not deemed medically necessary) is part of the standardized code set maintained by X12 and mandated for use in HIPAA-compliant electronic healthcare transactions. This code appears on Explanation of Benefits (EOB) and Electronic Remittance Advice (ERA) documents to explain claim adjustments. This code is used in various claim processing scenarios and requires review of the specific context and accompanying remark codes to fully understand the adjustment reason.
🔍 Common Causes
- Claim processing issue related to treatment not deemed medically necessary
- Payer policy or contract provision applied
- Service or billing does not meet payer requirements
- Additional review or documentation needed
- Plan-specific limitation or restriction applies
✅ Step-by-Step Solution
Review Denial Details
Carefully review the complete Explanation of Benefits (EOB) or Electronic Remittance Advice (ERA) to understand the specific reason code 58 was applied.
Gather Information
Collect all relevant documentation: original claim, medical records, authorization numbers, patient demographics, and any payer correspondence.
Contact Payer
Call the payer's provider services line with claim number and code 58. Ask for detailed explanation and specific steps to resolve.
Take Corrective Action
Based on payer guidance, either: correct and resubmit the claim, submit additional documentation, file a formal appeal, or bill the patient as appropriate.
Document Resolution
Keep detailed notes of all actions taken, payer communications, and outcome. Update procedures to prevent recurrence.
📋 Evidence & Documentation Checklist
📞 Insurance Company Call Script
Use these specific questions when contacting the payer:
- I'm calling regarding claim number [CLAIM#] which received adjustment code 58. Can you provide additional details about this adjustment?
- What specific documentation or information would help resolve this issue?
- What corrective action is needed to resolve this?
- Can you provide a reference number for this call?
- Is there anything else I should know about preventing this issue in the future?
🛡️ Prevention Tips
- Verify all claim information before submission
- Stay current on payer-specific policies and requirements
- Implement pre-submission claim review process
- Train staff on common denial codes and prevention
- Monitor denial reports to identify trends early
❓ Frequently Asked Questions
What does CARC code 58 mean?
This code indicates: treatment not deemed medically necessary. This is a standard claim adjustment reason code used to explain why the claim was processed differently than billed.
Is CARC 58 appealable?
Yes, CARC code 58 (Treatment not deemed medically necessary) is appealable. Carefully review the complete Explanation of Benefits (EOB) or Electronic Remittance Advice (ERA) to understand the specific reason code 58 was applied.
How do I fix CARC code 58?
The first step is: Review Denial Details - Carefully review the complete Explanation of Benefits (EOB) or Electronic Remittance Advice (ERA) to understand the specific reason code 58 was applied.. Then: Gather Information - Collect all relevant documentation: original claim, medical records, authorization numbers, patient ...
What are common causes of CARC 58?
The most common causes include: Claim processing issue related to treatment not deemed medically necessary; Payer policy or contract provision applied; Service or billing does not meet payer requirements.
Sources & Attribution
- X12 External Code List - CARC (Claim Adjustment Reason Codes) Version 34.0
- CMS Medicare Claims Processing Manual
- HIPAA Transaction and Code Set Standards - 45 CFR Parts 160 and 162
- Washington Publishing Company (WPC) - Official X12 Code List Maintainer
Last Updated: November 1, 2025
Update Cycle: Quarterly (March, July, November)
⚠️ Important Disclaimer
This information is provided for educational purposes only and should not be considered medical, billing, or legal advice. Always verify code interpretations with the specific payer and consult with qualified billing professionals. Code definitions, policies, and payer-specific guidelines may vary and are subject to change without notice. For the most current information, always refer to the latest X12 External Code List and payer-specific policies.