ICD-10-CM Code First Notes ICD-10-CM
A Code First note means the underlying condition named in the note is sequenced before this code. The FY 2027 Tabular List has 810 Code First Notes; 600 of them name other codes, with 736 references to 429 distinct codes, categories and ranges. Pick a chapter below to see every note in it, by the code that carries the note or by the code it names.
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. ICD-10-CM requires the underlying condition to be sequenced first, if applicable, followed by the manifestation. Wherever such a combination exists, there is a "code first" note at the manifestation code and a "use additional code" note at the etiology code. Manifestation codes titled "in diseases classified elsewhere" are never permitted as the first-listed or principal diagnosis. "Code first" notes are also used as sequencing rules for certain codes that are not part of an etiology/manifestation combination (Section I.B.7).
Code First Notes by Chapter 22 chapters
“References to its codes” counts notes anywhere in the Tabular List that name a code in the chapter; “references in its notes” counts the codes named by notes printed in the chapter. Each chapter page shows both lists.
Questions About Code First Notes
What does a Code First note mean?
A Code First note means the underlying condition named in the note is sequenced before the code that carries the note. Under the etiology/manifestation convention, a “code first” note appears at the manifestation code and a “use additional code” note at the etiology code (Section I.A.13). The FY 2027 Tabular List has 810 of them; 600 name other codes, with 736 references to 429 distinct codes, categories and ranges.
Can a code with a Code First note be the principal diagnosis?
Not when it is a manifestation code. Codes titled “in diseases classified elsewhere” are never permitted as the first-listed or principal diagnosis; they must follow the underlying condition. The etiology and manifestation page lists them all.
Is Code First used only for manifestation codes?
No. “Code first” and “use additional code” notes are also used as sequencing rules for certain codes that are not part of an etiology/manifestation combination (Section I.A.13 and Section I.B.7, multiple coding for a single condition).
Official Sources & Methodology
Every note on these pages is loaded verbatim from the FY 2027 ICD-10-CM Tabular List. Code references inside the notes are matched against the FY 2027 code set, so every link opens a valid code; scope counts (“applies to N codes”) count the billable codes under the note’s chapter, block or category.
- CMS ICD-10-CM FilesThe Tabular List (XML) that every note, note type and code reference on ICD List comes from.
- ICD-10-CM Official Guidelines for Coding and Reporting FY 2027Section I.A, Conventions for the ICD-10-CM, defines each note type; the definitions on these pages follow its wording.
ICD List is not affiliated with CMS or NCHS. These pages are a coding reference; the Tabular List and the Official Guidelines remain the authority.
Related References
Source: FY 2027 ICD-10-CM Tabular List (CMS and NCHS) and the ICD-10-CM Official Guidelines for Coding and Reporting FY 2027, Section I.A. ICD List is not affiliated with CMS or NCHS.
