For FY2027 ICD-10-CM, CMS identifies October 1, 2026 through September 30, 2027 for discharges and patient encounters. Check the reporting setting and the relevant encounter or discharge date before opening a release.
The answer in one date table
Start with the date that governs the reporting context. The CDC/NCHS release page says the October 1, 2026 FY2027 ICD-10-CM release replaces the April 1, 2026 FY2026 release. CMS lists the FY2027 files for discharges and patient encounters from October 1, 2026 through September 30, 2027.
| Reporting situation | Relevant date | Reference release |
|---|---|---|
| Outpatient encounter on September 30, 2026 | September 30 encounter or service date | FY2026 April 1 update |
| Outpatient encounter on October 1, 2026 | October 1 encounter or service date | FY2027 October 1 release |
| Inpatient hospital stay crossing the changeover, discharged October 1 | October 1 discharge date for the inpatient facility report | FY2027 October 1 release |
These are release-selection illustrations, not patient-specific code assignments or payment determinations. Confirm the setting and the applicable reporting instructions before applying the table to real work.
Source: CDC/NCHS: ICD-10-CM FY2026 and FY2027 release periods
For an outpatient encounter, look at when the service occurred
The date you research a code is not necessarily the date of the service. A September 30, 2026 outpatient encounter remains in the prior release period even if someone opens the record or prepares a claim in October. An October 1 encounter falls in the FY2027 period. CMS labels the FY2026 April 1 files for patient encounters through September 30, 2026 and the FY2027 files for encounters beginning October 1.
This is why a search result marked “current” can be misleading for historical work. Record the encounter date beside the classification and release. Then open the versioned FY2027 ICD-10-CM reference when that is the applicable release, and continue from the documented term through the Index and Tabular List. Our lookup guide explains that verification path.
Source: CMS: FY2026 April and FY2027 ICD-10-CM files and applicability
For an inpatient hospital report, check the discharge date
For the inpatient hospital reporting context described by CMS, the discharge date determines the release at this annual boundary. If an inpatient stay began before October 1 but the discharge occurred on October 1, the FY2027 files apply to that discharge. The admission date alone does not move the discharge into the FY2026 file period.
This distinction concerns which version of ICD-10-CM to consult. It does not decide a principal diagnosis, an additional diagnosis, a procedure code, or a payer outcome. The FY2027 official guidelines have separate inpatient and outpatient reporting sections; review the section that applies after establishing the release.
Source: CMS: FY2026 April and FY2027 ICD-10-CM files and applicability
Do not overlook the April 2026 FY2026 update
“FY2026” is a fiscal-year label, not a single undated download. CDC/NCHS identifies an April 1, 2026 FY2026 release for services through September 30, 2026, followed by the FY2027 release beginning October 1. CMS likewise lists the April 1, 2026 FY2026 files and their applicable encounter and discharge period. For a September 2026 historical lookup, identify that April update before comparing a code title or instruction with FY2027.
If a local list or saved link lacks the release date, return to the versioned source library and the CDC/NCHS file page. The FY2027 addenda checklist helps separate a genuine revision from a different release label.
Source: CDC/NCHS: ICD-10-CM FY2026 and FY2027 release periods
A four-step release check before selecting a code
- Identify the context. Is this an outpatient encounter or inpatient hospital discharge, and which reporting rules apply?
- Record the governing date. Keep the service or encounter date, or the inpatient discharge date, with the work item.
- Open the matching official files. Use the CDC/NCHS and CMS release pages to confirm the effective period and any later update.
- Verify the actual assignment separately. Follow the documented term through the Alphabetic Index, then read the full Tabular List entry and applicable guidelines.
Source: CMS: FY2027 ICD-10-CM Official Guidelines for Coding and Reporting
Common questions
Does the date I submit a claim choose the ICD-10-CM release?
No. The CMS release periods are stated for discharges and patient encounters. First establish the applicable service, encounter, or inpatient discharge date and setting; a later submission or lookup date does not by itself change the historical release.
Which release applies if an inpatient stay began in September but discharge was October 1?
For the inpatient hospital discharge context on the CMS ICD-10 files page, October 1, 2026 falls in the FY2027 release period. Verify the setting and full guidelines before assigning any diagnosis code.
Which FY2026 files cover a September 30, 2026 encounter?
CDC/NCHS identifies the April 1, 2026 FY2026 update for services through September 30, 2026. CMS lists the same period for its April 2026 files.
Is ICD-10-PCS covered by this date guide?
This guide concerns ICD-10-CM diagnosis releases. CMS publishes ICD-10-PCS inpatient procedure files separately; use the applicable CMS PCS files and guidance for that classification.
Sources & editorial notes
- CDC/NCHS: ICD-10-CM FY2026 and FY2027 release periods
- CMS: FY2026 April and FY2027 ICD-10-CM files and applicability
- CMS: FY2027 ICD-10-CM Official Guidelines for Coding and Reporting
Scope: U.S. ICD-10-CM diagnosis classification; FY2026 April 1 and FY2027 October 1 releases. Educational reference content, prepared with AI assistance; not independently reviewed by a credentialed clinical coding specialist. Verify official instructions and the applicable documentation before assigning codes. Our editorial approach.
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