Y99.9
Unspecified external cause status
BillableComplete code, valid to report
Y99.9 (also written Y999) is a billable ICD-10-CM diagnosis code for unspecified external cause status. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 5 codes in category Y99 (External cause status).
Guidelines tips
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
An external cause code is never a principal or first-listed diagnosis. Its 7th character is assigned for each encounter and should match the injury or condition code.
Only one Y99 code is recorded, at the initial encounter. It does not apply to poisonings, adverse effects, misadventures or late effects, and Y99.9 is not used when the status is not stated.
Notes
Inherited from Y99 External cause status
- A single code from category Y99 should be used in conjunction with the external cause code(s) assigned to a record to indicate the status of the person at the time the event occurred.
Also from chapter/block level (2 notes)
Inherited from Y90–Y99 Supplementary factors related to causes of morbidity classified elsewhere
- These categories may be used to provide supplementary information concerning causes of morbidity. They are not to be used for single-condition coding.
Inherited from Chapter 20 External causes of morbidity
- This chapter permits the classification of environmental events and circumstances as the cause of injury, and other adverse effects. Where a code from this section is applicable, it is intended that it shall be used secondary to a code from another chapter of the Classification indicating the nature of the condition. Most often, the condition will be classifiable to Chapter 19, Injury, poisoning and certain other consequences of external causes (S00-T88). Other conditions that may be stated to be due to external causes are classified in Chapters I to XVIII. For these conditions, codes from Chapter 20 should be used to provide additional information as to the cause of the condition.