The ICD-10-CM Official Guidelines for Coding and Reporting sets the precedent of rules that all diagnostic coders must abide by. Section I.C. covers the chapter-specific guidelines. These offer detailed information about various conditions that require more thorough reporting guidance than the general guidelines provide. Reading the guidelines in their entirety is incredibly important, but this series of articles aims to summarize and highlight key points. This article will break down the official guidelines for Chapters 17–20.

As always, both current and previous versions of the ICD-10-CM guidelines are stored on the CMS website. Make sure to use the correct version when reporting retrospective claims or conducting audits of previous years. Coders should also use Tabular List and National Correct Coding Initiative edits in tandem with these guidelines to more closely align with national coding requirements.

• Chapter 17: Congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
• Chapter 18: Symptoms, signs, and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)
• Chapter 19: Injury, poisoning, and certain other consequences of external causes (S00-T88)
• Chapter 20: External Causes of Morbidity (V00-Y99)