FY2027 ICD-10-CM reference
Q21.20: Atrioventricular septal defect, unspecified as to partial or complete
By the HCC Buddy Coding Team
The official ICD-10-CM descriptor is Atrioventricular septal defect, unspecified as to partial or complete. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Billable code. Verified against the official FY2027 order file.
FY2027 Tabular instructions
Instructions below include applicable chapter, section and parent-code notes. Each note identifies where it appears in the official source.
Instructional note
Codes from this chapter are not for use on maternal records
Source: Q00-QA1 (chapter, inherited).
Excludes2
inborn errors of metabolism (E70-E88)
Source: Q00-QA1 (chapter, inherited).
Excludes1
acquired cardiac septal defect (I51.0)
Source: Q21 (category, inherited).
Instructional note
Atrioventricular canal defect
Source: Q21.2 (self, inherited).
Instructional note
Endocardial cushion defect
Source: Q21.2 (self, inherited).
Instructional note
Ostium primum atrial septal defect (type I)
Source: Q21.2 (self, inherited).
Instructional note
Atrioventricular canal, NOS
Source: Q21.20 (self, direct).
Instructional note
Endocardial cushion defect NOS
Source: Q21.20 (self, direct).
Instructional note
Ostium primum atrial septal defect (type I) NOS
Source: Q21.20 (self, direct).
Compare the FY2027 additions, removals and billable-status changes
What does Q21.20 mean in FY2027?
The official ICD-10-CM descriptor is Atrioventricular septal defect, unspecified as to partial or complete. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Is Q21.20 billable in FY2027?
The FY2027 order file marks Q21.20 as billable. Check the complete Tabular instructions and documentation before assigning it.
Does Q21.20 map to an HCC?
Q21.20 has no CMS-HCC V28 category in the CMS 2027 Initial ICD-10-CM Mappings (payment year 2027, 2026 dates of service). Under the PY2026 CMS mapping; CMS 2027 initial file unchanged: no ESRD category; RxHCC HCC 191. Coefficients for these models are pending verification for payment year 2027. CMS-HCC V24, PACE and HHS-HCC mappings are still pending verification for FY2027.
Source: CMS FY2027 ICD-10-CM order file. Read the FY2027 Official Guidelines.
Review the FY2026 April edition