I.A.18
Default codes
A code listed next to a main term in the ICD-10-CM Alphabetic Index is referred to as a default code. The default code represents that condition that is most commonly associated with the main term or is the unspecified code for the condition. 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.
ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026 (effective October 1, 2025). Published by CMS and NCHS. Reproduced for reference — always verify against the official CMS release.