ICD-10 updates and behavioral health claim denials

Why behavioral health practices face compounded ICD-10-CM billing risk every October

Every October 1, ICD-10-CM codes update across every specialty.¹ For many practices, the changes that affect their highest-volume diagnoses are infrequent enough to manage. However, behavioral health practices — and primary care practices who regularly document mental health diagnoses — experience more frequent and extensive updates to their most used codes, requiring continuous staff training and increasing the risk of documentation and billing errors.

Behavioral health billing is structurally more complex than most specialties. Services are documented through time-based codes, subjective clinical notes, and treatment plans that evolve over weeks or months — and payers scrutinize them accordingly. Annual code transitions compound that complexity. Outdated codes look correct in a system that hasn't been updated. The denial is the first signal something is wrong.

Since 2022, the APA has been issuing annual DSM-5-TR coding supplements every September, introducing behavioral-health-specific code changes that take effect on the same October 1 deadline. This doubles the compliance workload for behavioral health practices, who must review, cross-reference, and implement changes from both the standard ICD-10-CM updates and the DSM-5-TR behavioral health-specific updates — often affecting the same diagnosis codes they bill most frequently.

Miss one updated code, and the problems are felt immediately and quickly compound — in the denial queue and rework backlog and in a collections cycle that runs longer than it should while your team chases claims that were clean before October 1.

Behavioral health billing is structurally more complex than most specialties. Services are documented through time-based codes, subjective clinical notes, and treatment plans that evolve over weeks or months — and payers scrutinize them accordingly. Annual code transitions compound that complexity. Outdated codes look correct in a system that hasn't been updated. The denial is the first signal something is wrong.

What changed in the FY2026 ICD-10-CM update for mental health diagnoses

The FY2026 update has required greater specificity for major depressive disorder, anxiety, and substance use disorder codes. These changes land squarely in the diagnostic categories that behavioral health and primary care practices bill most. The update expands the F32–F33 major depressive disorder series with added symptom severity and episode descriptors, refines substance use disorder remission statuses, and broadens anxiety disorder codes including panic disorder and generalized anxiety in adults.² Claims submitted with the prior version of a code generate a denial regardless of how thorough the clinical note behind it is.

Four billing risks that follow outdated behavioral health codes

1. Denials on your most frequently billed diagnoses

When F32 and F33 codes require added severity specificity and a practice's code library still reflects the prior version, every major depressive disorder claim submitted with the old code is at risk. The clinical work is sound, but the denial is a coding problem, often missed until it surfaces in a remittance.

2. Revenue that walks out through non-resubmission

Industry reports suggest that up to 20% of behavioral health claims may be denied due to incorrect coding, with a significant portion never resubmitted — causing revenue leakage for providers and care gaps for patients.³ Code-transition denials tend to surface weeks after the October 1 effective date, by which point a meaningful volume of claims has already accumulated. For smaller practices without a dedicated billing team, the backlog arrives faster than the bandwidth to address it.

3. Rework that lands on the clinician

In small group and telehealth behavioral health practices, appeals and resubmissions don't go to a revenue cycle department. They go to the provider or the practice manager — after hours, between patients, on the margins of a day that was already full. The downstream cost of a code-set gap rarely gets attributed to its source.

4. Documentation misalignment on collaborative care billing

Collaborative care CPT codes require full consistency across diagnosis codes, clinical notes, and service codes. An outdated diagnosis code in a high-volume category doesn't just affect the diagnosis line — it can undermine the integrity of the entire claim.

How to audit your behavioral health code set before the next denial cycle

The best way to prevent post-October 1 denials is to audit your code set now — before outdated codes enter your billing system. A proactive review helps you identify gaps, correct errors, and ensure your documentation and billing workflows are aligned with the latest requirements.

Step 1: Check your active code library against current ICD-10-CM requirements

Confirm that your diagnostic codes for major depressive disorder, substance use disorders, and anxiety disorders reflect the post-October 1, 2025, specificity requirements. If your platform requires manual updates, start here ASAP.

Step 2: Ask your EHR vendor when the code library was last updated

If behavioral health wasn't a primary configuration focus during your EHR implementation, the code set may not reflect recent changes. Before the September 2026 supplement publishes, confirm with your vendor that updates will be in place before October 1.

Step 3: Pull a targeted claims review for October–December 2025

Filter denials from the October-December window by behavioral health diagnosis codes. A spike in the F32–F33 or substance use disorder categories is a signal that outdated codes are active. Some of those claims may still be recoverable through resubmission.

Step 4: Put October 1 on your annual compliance calendar

The supplement publishes every September. The effective date is every October  1. This is a recurring obligation, and practices can handle it cleanly by makiing it a standing process.

Why your EHR’s code update timing directly impacts your revenue

A lot of practices don't choose their EHR with the DSM-5-TR supplement cycle in mind. Instead, they find out their code set is outdated through a denial. The average in-network denial rate hit 19% in 2024, with behavioral health among the most denial-heavy specialties⁴ — and code-set gaps from annual transitions are among the most preventable sources of those rejections.

athenaOne® helps practices avoid these gaps by updating three times a year, to incorporate ICD-10-CM changes in step with effective dates. For behavioral health and primary care practices, that means the code set in use on October 1 reflects what payers require on October 1 — without a manual update process, vendor call, or waiting for the remittance to surface the problem.

The September 2026 supplement will publish on schedule. October 1 will arrive on schedule. The practices that are ready before that date will have fewer operational problem to manage — and one fewer source of preventable revenue loss.

Learn how athenaOne® for Behavioral Health updates automatically with ICD-10-CM and DSM-5-TR changes, keeping your code library current without manual intervention.