F99 ICD-10-CM Code: Mental disorder, not otherwise specified
F99 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Unspecified mental disorder (F99)
F99
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMental disorder, not otherwise specified
A mental health disorder that cannot be classified into any other specific mental disorder category.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Mental illness NOS
Excludes 2
Official- symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)Inherited from F01-F99
Related Codes
No related codes are included in this display for F99. Check the Code Book for the complete code path.
Includes
Official- disorders of psychological developmentInherited from F01-F99
Excludes 1
Official- unspecified mental disorder due to known physiological condition (F09)
Code First
OfficialNo Code First sequencing instructions are included in this display for F99. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for F99. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for F99. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is F99 an HCC code?
No. F99 is a billable ICD-10-CM code with no mapping under the current CMS-HCC V28 community payment model, and none under the ESRD, Part D RxHCC, or HHS-HCC models.
- Code
- F99
- Description
- Mental disorder, not otherwise specified
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF reference coefficient
- —
- Billable
- Yes
- Payment year
- 2026
Coder workflow notes
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What This Code Means
F99 is the ICD-10-CM diagnosis code for mental disorder, not otherwise specified. A mental health disorder that cannot be classified into any other specific mental disorder category. F99 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering unspecified mental disorder (f99).
F99 is a billable ICD-10-CM code, but no current CMS-HCC V28 community payment mapping is shown, and none under the ESRD, Part D RxHCC, or HHS-HCC models. Do not assign risk adjustment value from this page when no source-backed mapping is shown; verify the applicable model and payment year.
This is a last-resort code; ensure all documentation has been reviewed for a more specific mental health diagnosis.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for F99 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a last-resort code; ensure all documentation has been reviewed for a more specific mental health diagnosis
- •Consider querying the provider if symptoms are documented but a specific diagnosis is not assigned
Excludes 1, Do NOT code together
- unspecified mental disorder due to known physiological condition (F09)