M20.4 ICD-10-CM Code: Other hammer toe(s) (acquired)

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for M20.4 in the official ICD-10-CM tabular list, quoted as published.

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

Notes without a marker are published on M20.4 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for M20.4

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

Before you code M20.4

1. M20.4 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

   ReviewM20.40, M20.41, M20.42

   See the relationships section · Guide: How to choose an ICD-10-CM code →

2. “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 M20.4; 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).

   ReviewM20.1, M20.2, M20.3

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

3. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with M20.4. 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 one of the more specific codes beneath M20.4?
   Yes → Select that code and continue the checks below on its own page.
   No → M20.4 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewM20.40, M20.41, M20.42

2. Does the documentation support a condition named in M20.4’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.

   ReviewZ89, Q71.3, Q72.3, Q66, Q74

Consider M20.4. 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 M20.4(3 notes)

  Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with M20.4: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

  CompareZ89, Q71.3, Q72.3, Q66, Q74

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

• Excludes2 — not part of M20.4(1 note)

  Coding workflow: The conditions named in this note are not included in M20.4. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

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

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.

Don’t confuse M20.4 with…

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

The codes most likely to be picked instead of M20.4 — 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.

• Z89— 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 acquired absence of fingers and toes moves the case to Z89; the two are not reported together unless documented as unrelated.

  Full comparison: M20.4 vs Z89 →

• Q71.3— 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 congenital absence of fingers and toes moves the case to Q71.3; the two are not reported together unless documented as unrelated.

  Full comparison: M20.4 vs Q71.3 →

• Q72.3— 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 congenital absence of fingers and toes moves the case to Q72.3; the two are not reported together unless documented as unrelated.

  Full comparison: M20.4 vs Q72.3 →

• Q66— 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 congenital deformities and malformations of fingers and toes moves the case to Q66; the two are not reported together unless documented as unrelated.

  Full comparison: M20.4 vs Q66 →

• Q68— 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 congenital deformities and malformations of fingers and toes moves the case to Q68; the two are not reported together unless documented as unrelated.

  Full comparison: M20.4 vs Q68 →

• Q70— 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 congenital deformities and malformations of fingers and toes moves the case to Q70; the two are not reported together unless documented as unrelated.

  Full comparison: M20.4 vs Q70 →

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

• Not billable as written — a more specific code is required: M20.40, M20.41, M20.42.

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 M20.4 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 1 Excludes1 note: Z89 — Acquired absence of limb (via M20.-).

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

Referenced by 5 Excludes2 notes: M21 — Other acquired deformities of limbs (via M20.-), M21.6 — Other acquired deformities of foot (via M20.-), M24.5 — Contracture of joint (via M20.-), M25 — Other joint disorder, not elsewhere classified (via M20.-), M95 — Other acquired deformities of musculoskeletal system and connective tissue (via M20.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Related Codes

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Deformity”; these codes share that main term but sit in a different category of the Tabular List.

K22.89 — Other specified disease of esophagus (esophagus, acquired), K31.2 — Hourglass stricture and stenosis of stomach (cascade, stomach), K31.89 — Other diseases of stomach and duodenum (duodenal bulb), K62.89 — Other specified diseases of anus and rectum (anus), K63.89 — Other specified diseases of intestine (ileocecal), K76.89 — Other specified diseases of liver (liver, acquired), K82.8 — Other specified diseases of gallbladder (cystic duct, acquired), K83.8 — Other specified diseases of biliary tract (bile duct, acquired), K86.89 — Other specified diseases of pancreas (pancreas, acquired), L60.8 — Other nail disorders (nail), M21.00 — Valgus deformity, not elsewhere classified, unspecified site (valgus NEC), M21.02 — Valgus deformity, not elsewhere classified, elbow (valgus NEC, elbow), M21.05 — Valgus deformity, not elsewhere classified, hip (valgus NEC, hip), M21.06 — Valgus deformity, not elsewhere classified, knee (valgus NEC, knee), M21.07 — Valgus deformity, not elsewhere classified, ankle (valgus NEC, ankle), M21.10 — Varus deformity, not elsewhere classified, unspecified site (varus NEC), M21.12 — Varus deformity, not elsewhere classified, elbow (varus NEC, elbow), M21.15 — Varus deformity, not elsewhere classified, hip (varus NEC, hip), M21.16 — Varus deformity, not elsewhere classified, knee (varus NEC, knee), M21.17 — Varus deformity, not elsewhere classified, ankle (varus NEC, ankle), +223 more

Contextual Map

Every relationship of M20.4 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 M20.4 with these 6 related codes in Claim Check

Hierarchy

• M00-M99 — Chapter 13: Diseases of the Musculoskeletal System and Connective Tissue (M00-M99) (M00-M99)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M00-M25 — Arthropathies[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20-M25 — Other joint disorders[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes1 notes

• Z89 — Acquired absence of limb[Excludes1](via M20.-): “acquired deformities of limbs (M20-M21)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes2 notes

• M21 — Other acquired deformities of limbs[Excludes2](via M20.-): “acquired deformities of fingers or toes (M20.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• M21.6 — Other acquired deformities of foot[Excludes2](via M20.-): “deformities of toe (acquired) (M20.1-M20.6-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• M24.5 — Contracture of joint[Excludes2](via M20.-): “acquired deformities of limbs (M20-M21)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• M25 — Other joint disorder, not elsewhere classified[Excludes2](via M20.-): “acquired deformities of limb (M20-M21)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• M95 — Other acquired deformities of musculoskeletal system and connective tissue[Excludes2](via M20.-): “acquired deformities of limbs (M20-M21)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Nearest codes (40)

• M20 — Acquired deformities of fingers and toes[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20.01 — Mallet finger[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20.011 — Mallet finger of right finger(s)[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20.012 — Mallet finger of left finger(s)[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20.019 — Mallet finger of unspecified finger(s)[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20.02 — Boutonnière deformity[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20.021 — Boutonnière deformity of right finger(s)[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• M20.022 — Boutonnière deformity of left finger(s)[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

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

Common coding questions

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

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 M20.4 in its code family, with their registry titles.

• M20.22 — Hallux rigidus, left foot
• M20.3 — Hallux varus (acquired)
• M20.30 — Hallux varus (acquired), unspecified foot
• M20.31 — Hallux varus (acquired), right foot
• M20.32 — Hallux varus (acquired), left foot
• M20.40 — Other hammer toe(s) (acquired), unspecified foot
• M20.41 — Other hammer toe(s) (acquired), right foot
• M20.42 — Other hammer toe(s) (acquired), left foot
• M20.5 — Other deformities of toe(s) (acquired)
• M20.5X — Other deformities of toe(s) (acquired)

View all codes in the M20 family