DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

R99 diagnosis code · Billable category · FY2027

R99 Ill-defined and unknown cause of mortality

  • Billable
  • Not CC/MCC
  • POA reported

R99 ICD-10 code: a billable diagnosis code in FY2027; the category has no subdivisions.

Where it sits

  1. Chapter 18 Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)
  2. R99 Ill-defined and unknown cause of mortality (R99)
  3. R99 Ill-defined and unknown cause of mortality
CC / MCC
Neither
MS-DRG
951
HCC V28
–
POA
Reported
Code Editor
–
Index entries
5

Instructions

At R99

Inclusion terms

  • Death (unexplained) NOS
  • Unspecified cause of mortality

Notes that also apply

Chapter 18 instructions (Notes 9, Excludes2 4): printed on the chapter 18 page.

Index entries

  • Cot death → R99
  • Crib death → R99
  • Death (cause unknown) (of) (unexplained) (unspecified cause) → R99
  • Sudden infant death syndrome (SIDS) → R99
  • Syndromecrib death → R99

NCHS Alphabetic Index. Index first, then the Tabular List.

Medicare grouping and edits

CMS files for R99
CC / MCCNeither
Appendix BMDC 23 Factors Influencing Health Status and Other Contacts with Health Services, MS-DRG 951 (Other Factors Influencing Health Status…)
Code Editor–
POAReported
HCC V28–

CMS: MS-DRG v44 (Appendix B, C), MCE v44, POA list FY2027, 2027 Initial ICD-10-CM Mappings. What the rows mean.