ICD-10-CM diagnosis code
T23.639D Corrosion of second degree of unspecified multiple fingers (nail), not including thumb, subsequent encounter
- Billable
- Yes, a complete code (FY2026)
Encounter (7th character)
This code is for a subsequent encounter: active treatment is complete and the patient is being seen during healing or recovery (for example a cast change, medication adjustment or follow-up visit).
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Other codes in T23
648 complete codes in this category.
- T23.631DCorrosion of second degree of multiple right fingers (nail), not including thumb, subsequent encounter
- T23.631SCorrosion of second degree of multiple right fingers (nail), not including thumb, sequela
- T23.632ACorrosion of second degree of multiple left fingers (nail), not including thumb, initial encounter
- T23.632DCorrosion of second degree of multiple left fingers (nail), not including thumb, subsequent encounter
- T23.632SCorrosion of second degree of multiple left fingers (nail), not including thumb, sequela
- T23.639ACorrosion of second degree of unspecified multiple fingers (nail), not including thumb, initial encounter
- T23.639DCorrosion of second degree of unspecified multiple fingers (nail), not including thumb, subsequent encounter
- T23.639SCorrosion of second degree of unspecified multiple fingers (nail), not including thumb, sequela
- T23.641ACorrosion of second degree of multiple right fingers (nail), including thumb, initial encounter
- T23.641DCorrosion of second degree of multiple right fingers (nail), including thumb, subsequent encounter
- T23.641SCorrosion of second degree of multiple right fingers (nail), including thumb, sequela
- T23.642ACorrosion of second degree of multiple left fingers (nail), including thumb, initial encounter
Documentation tips
- Make sure the note supports every element of the title, “Corrosion of second degree of unspecified multiple fingers (nail), not including thumb, subsequent encounter”: each detail in it should be traceable to the history, examination or assessment.
- Code to the highest specificity the documentation supports. If a detail is missing from the note, add it to the note rather than choosing a less specific code by default.
- Check the Tabular List and official guidelines for instructional notes (“code first”, “use additional code”, Excludes1/Excludes2) that apply to T23.
The international WHO ICD-10 also has T23, with its inclusion and exclusion notes; titles and detail can differ from ICD-10-CM.
ICD-10-CM is developed by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, and is based on the WHO ICD-10. Codes and titles are reproduced unchanged from the FY2026 code list (effective 1 October 2025). Their use here does not imply endorsement by CDC, HHS or the U.S. Government. Changes effective on or after 1 October 2026 may not be reflected yet; check the current release at cdc.gov or cms.gov before submitting claims.
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