ICD-10 Code Auditor

ICD-10-CM Official Coding Guidelines (FY2026)

What Are the ICD 10 Coding Guidelines?

The ICD 10 coding guidelines (formally titled "ICD-10-CM Official Guidelines for Coding and Reporting") are the authoritative rules for assigning ICD-10-CM diagnosis codes. Published jointly by the American Hospital Association (AHA), American Health Information Management Association (AHIMA), Centers for Medicare & Medicaid Services (CMS), and the National Center for Health Statistics (NCHS), these guidelines are updated annually to reflect new codes and coding conventions.

The ICD 10 coding guidelines 2026 (FY2026) are effective October 1, 2025 through September 30, 2026. They include new codes, revised code descriptions, and updated sequencing instructions for accurate diagnosis coding.

Types of Rules in the ICD 10 CM Official Guidelines

The ICD 10 CM official guidelines cover several categories of coding rules. Understanding these rule types is essential for accurate medical coding and compliance:

• 1. Sequencing Rules (Code First / Use Additional Code) — Instructions that specify the order in which codes must appear. "Code First" means the underlying condition must be listed before the manifestation. "Use Additional Code" prompts coders to add secondary codes for complete documentation.
• 2. Excludes Notes (Excludes1 / Excludes2) — Excludes1 indicates two conditions cannot be coded together because they are mutually exclusive. Excludes2 indicates a condition is "not included here" but may be coded together if both conditions exist.
• 3. Laterality Requirements — Many ICD-10-CM codes require specification of which side of the body is affected (right, left, bilateral, or unspecified). Using the most specific laterality code is required when documentation supports it.
• 4. Specificity Rules — Codes must be assigned to the highest level of specificity available. A 4th, 5th, 6th, or 7th character must be used when the classification provides them and documentation supports that level of detail.
• 5. Combination Codes — Single codes that classify two diagnoses, a diagnosis with a secondary process, or a diagnosis with a complication. When a combination code exists, it should be used instead of multiple separate codes.
• 6. Gender-Specific Codes — Certain diagnosis codes are only valid for male or female patients. Assigning a gender-specific code to the wrong patient sex creates a coding conflict.

How Our Auditor Validates Against These Guidelines

Our ICD 10 coding guidelines auditor automatically checks your encounter-level codes against the ICD 10 CM official guidelines. For each code entered, the tool validates:

• ✓ Code First compliance — Flags codes that require an underlying etiology code to be sequenced first
• ✓ Use Additional Code requirements — Identifies when secondary codes are required but missing
• ✓ Excludes1 conflicts — Detects mutually exclusive code pairs that violate official guidelines
• ✓ Laterality and specificity gaps — Alerts when a more specific code exists and should be used
• ✓ Gender conflicts — Ensures codes match the patient's documented sex
• ✓ Active vs History conflicts — Prevents coding an active condition alongside its history code

Note: This tool validates ICD-10-CM (diagnosis) codes only. ICD-10-PCS (procedure) code validation is not currently supported. For detailed guidelines by topic, see our ICD-10 Guidelines reference.