U.S. ICD-10-CM · FY 2027

R99 ICD-10-CM Code: Ill-defined and unknown cause of mortality

A clear reference for the official code description, hierarchy, and related coding information from the FY 2027 U.S. release.

Code definition

Official description

R99

Ill-defined and unknown cause of mortality

ICD-10-CM diagnosis code · United States clinical modification

Classification

Where R99 sits

  1. 1

    Chapter 18

    Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)

  2. 2

    Section

    Ill-defined and unknown cause of mortality (R99)

  3. 3

    Category R99

    Ill-defined and unknown cause of mortality

  4. 4

    Code R99

    Ill-defined and unknown cause of mortality

Documentation details

Notes for this code

Inclusion terms

  • Death (unexplained) NOS
  • Unspecified cause of mortality

Code first

No “code first” instruction is listed for R99.

Use additional code

No “use additional code” instruction is listed for R99.

Excludes1

Conditions that should not be reported together with this code.

No Excludes1 note is listed for R99.

Excludes2

Conditions not included here that may be reported separately when present.

No Excludes2 note is listed for R99.

Transparency

Source and release

Data release

U.S. ICD-10-CM · FY 2027

Effective date

Oct 1, 2026

Publisher

Vero Scribe Inc.

This reference is generated from Vero’s ICD-10-CM description, hierarchy, and code-note dataset. The visible content and structured data share that source.

Review the CDC/NCHS ICD-10-CM source

Code-specific guidance

Frequently asked questions

What does ICD-10-CM code R99 mean?

R99 is the FY 2027 U.S. ICD-10-CM code for “Ill-defined and unknown cause of mortality.”

Is R99 a billable or specific ICD-10-CM code?

Yes. In the FY 2027 reference data used on this page, R99 has no child codes and is presented as a billable/specific code. Always confirm the active code set and payer requirements before use.

Where is R99 located in ICD-10-CM?

R99 is listed in Chapter 18, Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99), within Ill-defined and unknown cause of mortality (R99) (R99–R99), under category R99, Ill-defined and unknown cause of mortality.

What coding notes are listed for R99?

Its listed inclusion terms are Death (unexplained) NOS; Unspecified cause of mortality. No code-first instruction is listed. No Excludes1 note is listed. No Excludes2 note is listed.

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