Y99.8 ICD-10-CM Code: Other external cause status

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Y99.8 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Coder workflow for Y99.8

MedCoder structured workflow — derived from this code’s own official record

Before you code Y99.8

1. “Other” (NEC) means the condition is specified in the record but no dedicated code captures it. Confirm the documented form is not one a sibling code names before settling on Y99.8; if the record states no specifics at all, the unspecified sibling applies instead. “Other” codes are for documented conditions the classification gives no specific code; “unspecified” codes are for records lacking the detail (Guidelines I.A.9.a, I.A.9.b).

   ReviewY99.0, Y99.1, Y99.2

   See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

2. An external cause code is reported in addition to the code for the injury or condition, never as the principal or first-listed diagnosis. Confirm the cause, intent, place of occurrence, activity and status where the record documents them, and assign the 7th character that matches the injury code. External cause coding guidelines (Guidelines I.C.20.a).

3. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with Y99.8. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

   See the official tabular notes

Choose the right path

1. Does the documentation support a condition named in Y99.8’s Excludes1 note?
   Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
   No → Continue.

   ReviewY99.0, Y99.1

Consider Y99.8. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Any detail beyond this code’s title

What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

• Excludes1 — check before selecting Y99.8(2 notes)

  Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with Y99.8: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

  CompareY99.0, Y99.1

  See the official tabular notes · Guidelines I.A.12.a

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Indexed As (16)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Circumstance phrases from the official ICD-10-CM External Cause of Injuries Index that map to this code.

• External cause status, child assisting in compensated work for family
• External cause status, family member assisting in compensated work for other family member
• External cause status, hobby not done for income
• External cause status, leisure activity
• External cause status, off-duty activity of military personnel
• External cause status, recreation or sport not for income or while a student
• External cause status, specified NEC
• External cause status, student activity
• Status of external cause, child assisting in compensated work for family
• Status of external cause, family member assisting in compensated work for other family member
• Status of external cause, hobby not done for income
• Status of external cause, leisure activity
• Status of external cause, off-duty activity of military personnel
• Status of external cause, recreation or sport not for income or while a student
• Status of external cause, specified NEC
• Status of external cause, student activity

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Don’t confuse Y99.8 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of Y99.8 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• Y99.0— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of civilian activity done for income or compensation moves the case to Y99.0; the two are not reported together unless documented as unrelated.

  Full comparison: Y99.8 vs Y99.0 →

• Y99.1— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of military activity moves the case to Y99.1; the two are not reported together unless documented as unrelated.

  Full comparison: Y99.8 vs Y99.1 →

• Y99.9— Specificity relationship (Review)

  Overlapping diagnoses in the same category.

  Overlapping codes in the same category — the documentation decides which is the more specific fit.

  What moves you there: A record that documents no more than “Unspecified external cause status” takes Y99.9; specificity in the record moves it back here.

  Full comparison: Y99.8 vs Y99.9 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• Principal-diagnosis restriction. External cause of morbidity codes (V, W, X and Y) describe the circumstance that caused an injury, not the condition treated. The Medicare Code Editor rejects them as a principal diagnosis; sequence the injury or condition first and report this code as secondary.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name Y99.8 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 2 Excludes1 notes: Y99.1 — Military activity, Y99.2 — Volunteer activity.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Clinical classification (AHRQ CCSR):EXT026 — External cause codes: activity codes.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (External cause codes: activity codes).

Y93.H1 — Activity, digging, shoveling and raking, Y93.H2 — Activity, gardening and landscaping, Y93.H3 — Activity, building and construction, Y93.H9 — Activity, other involving exterior property and land maintenance, building and construction, Y93.I1 — Activity, roller coaster riding, Y93.I9 — Activity, other involving external motion, Y93.J1 — Activity, piano playing, Y93.J2 — Activity, drum and other percussion instrument playing, Y93.J3 — Activity, string instrument playing, Y93.J4 — Activity, winds and brass instrument playing, Y93.K1 — Activity, walking an animal, Y93.K2 — Activity, milking an animal, Y93.K3 — Activity, grooming and shearing an animal, Y93.K9 — Activity, other involving animal care, Y93.L1 — Activity, splitting wood, Y93.L9 — Activity, other outdoor activity, Y99.0 — Civilian activity done for income or pay, Y99.1 — Military activity, Y99.2 — Volunteer activity, Y99.9 — Unspecified external cause status, +93 more

Contextual Map

Every relationship of Y99.8 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run Y99.8 with these 3 related codes in Claim Check

Hierarchy

• V00-Y99 — Chapter 20: External Causes of Morbidity (V00-Y99) (V00-Y99)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Y90-Y99 — Supplementary factors related to causes of morbidity classified elsewhere[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Excludes1

• Y99.0 — Civilian activity done for income or pay[Excludes1]: “civilian activity done for income or compensation (Y99.0)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• Y99.1 — Military activity[Excludes1]: “military activity (Y99.1)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes1 notes

• Y99.1 — Military activity[Excludes1]: “activity of off duty military personnel (Y99.8)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• Y99.2 — Volunteer activity[Excludes1]: “activity of child or other family member assisting in compensated work of other family member (Y99.8)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• EXT026 — External cause codes: activity codes[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

External cause index (16)

• External cause status, child assisting in compensated work for family[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• External cause status, family member assisting in compensated work for other family member[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• External cause status, hobby not done for income[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• External cause status, leisure activity[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• External cause status, off-duty activity of military personnel[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• External cause status, recreation or sport not for income or while a student[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• External cause status, specified NEC[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• External cause status, student activity[External cause term]— CMS External Cause of Injuries Index · icd10cm-fy2026
• and 8 more

Nearest codes

• Y99 — External cause status[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Y99.0 — Civilian activity done for income or pay[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Y99.1 — Military activity[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Y99.2 — Volunteer activity[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• Y99.9 — Unspecified external cause status[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Coding guidelines Official source data

ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Y99.8 in its code family, with their registry titles.

• Y99 — External cause status
• Y99.0 — Civilian activity done for income or pay
• Y99.1 — Military activity
• Y99.2 — Volunteer activity
• Y99.9 — Unspecified external cause status

View all codes in the Y99 family