Understanding Common Denial Codes in Behavioral Health

📅 January 10, 2026 ⏱️ 8 min read 🏷️ Denial Management
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If you're running a behavioral health practice in Illinois, you've likely encountered claim denials that seem confusing or arbitrary. Understanding what these denial codes mean—and more importantly, how to prevent them—can significantly impact your bottom line.

The Cost of Denials

According to the Healthcare Financial Management Association (HFMA), Illinois behavioral health practices see denial rates between 15-18%. Each denied claim costs an average of $25-$35 to rework, not including the lost revenue if the appeal fails.

Most Common Denial Codes

CO-4: The procedure code is inconsistent with the modifier used

What it means: The CPT code doesn't match the modifier. Common with telehealth (modifier 95/GT) and group therapy sessions.

Prevention: Verify modifier requirements for each payer before submission. BCBS IL and UHC have different telehealth modifier preferences.

CO-16: Claim/service lacks information needed for adjudication

What it means: Missing or invalid information—often related to prior authorization numbers or diagnosis codes.

Prevention: Implement a pre-submission checklist. Verify all required fields are completed, especially auth numbers for intensive outpatient (IOP) services.

CO-97: Payment adjusted based on medical necessity

What it means: The payer doesn't believe the service was medically necessary based on the documentation provided.

Prevention: Ensure clinical documentation clearly supports the level of care. Include specific symptoms, functional impairments, and treatment goals.

PR-204: This service is not covered under the member's plan

What it means: Eligibility verified, but the specific service isn't a covered benefit.

Prevention: Verify benefits before each session, especially for specialized services like psychological testing or EMDR.

Payer-Specific Patterns

BlueCross BlueShield Illinois

BCBS IL commonly denies claims for:

UnitedHealthcare

UHC's most common denial reasons include:

What To Do When Claims Age Past 60 Days

Once claims enter the 60-180 day "death zone", recovery rates drop significantly. At this point, internal billing teams are often too overwhelmed with current claims to give aged A/R the attention it needs.

This is where specialized A/R recovery becomes valuable. Rather than writing off these claims, a dedicated team can apply focused attention to recover what's rightfully owed to your practice.

Struggling with Aged Claims?

Our team specializes in recovering 60-180+ day aged A/R for Illinois behavioral health practices.

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Key Takeaways

  1. Track denial patterns by payer to identify systemic issues
  2. Implement pre-submission checklists to catch common errors
  3. Document thoroughly for medical necessity claims
  4. Don't ignore aged claims—they represent real revenue
  5. Consider specialized help for 60+ day aged A/R

Understanding denial codes is the first step toward reducing them. For more resources, check out our complete denial code glossary.