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Default codes

Official text from the FY2027 ICD-10-CM Official Guidelines for Coding and Reporting. The wording is quoted exactly.

Guidelines I.A.18

“A code listed next to a main term in the ICD-10-CM Alphabetic Index is referred to as a default code.”

“If a condition is documented in a medical record (for example, appendicitis) without any additional information, such as acute or chronic, the default code should be assigned.”

Where this applies

This is a general rule. It applies to code assignment everywhere, not to one code or group of codes.

Source: FY 2027 ICD-10-CM Official Guidelines for Coding and Reporting, effective October 1, 2026. Full Guidelines (PDF, CMS)