ICD-10-CM 2027 Changes: The Complete FY2027 Update Reference

The ICD-10-CM 2027 changes take effect October 1, 2026 and stay in force through September 30, 2027. CMS and the CDC's National Center for Health Statistics released the FY2027 files in June 2026. The update adds 190 new diagnosis codes, deletes 30, and revises four.

That is a quiet year by recent standards. FY2026 added 487. The volume drop matters less than where the changes landed, because several of this year's revisions are not new codes at all. They are Excludes note changes and Alphabetic Index reroutes, and those are the ones that break a coding edit without anyone noticing until the denials arrive.

This page is the reference. It covers the counts, the effective dates for both code sets, the additions worth building around, the non-code changes, the guideline revisions, and a readiness check to run before October 1.

FY2027 by the numbers

Code set	New	Deleted	Revised	Effective
ICD-10-CM (FY2027)	190	30	4	Oct 1, 2026 – Sep 30, 2027
ICD-10-CM (FY2026, prior year)	487	28	38	Oct 1, 2025 – Sep 30, 2026
ICD-10-PCS (FY2027)	101	38	3	Oct 1, 2026 – Mar 31, 2027

The FY2027 ICD-10-PCS set totals 79,256 codes. Fifty of the 101 additions sit in the New Technology section, spread across 13 tables, and CMS added one new table, XEZ, carrying 10 codes for other procedures involving physiological systems and anatomical regions.

A note on the count, because published recaps disagree

Several vendor and trade summaries of this update report 190 new codes. Others report 238. A few report a total change count of 228 without separating additions from deletions.

We report 190 new, 30 deleted and 4 revised because that figure is what the Society of Interventional Radiology and the RCM trade press both published against the June 2026 file release, and because it is internally consistent with the chapter-level breakdowns we have reviewed. Anyone who needs the number to be defensible in an audit setting should not take ours or anyone else's on trust. Download the 2027 Addendum from the CMS ICD-10 page and count the addition, deletion and revision rows directly. That file is the only arbiter, and the exercise takes about twenty minutes.

The reason to care: if your organization publishes a code-update summary internally, and the number in it does not match the addendum, every downstream readiness metric built on that summary inherits the error.

Two effective dates, not one

ICD-10-CM and ICD-10-PCS run on different update rhythms, and conflating them is a common source of go-live errors.

ICD-10-CM applies to discharges and patient encounters from October 1, 2026 through September 30, 2027. It runs the full fiscal year. There is a mid-year April cycle, but the April 1, 2026 release added no new diagnosis codes at all, only index, tabular and instructional note changes.

ICD-10-PCS applies to discharges from October 1, 2026 through March 31, 2027 only. CMS publishes a mid-year PCS update effective April 1 each year. The April 1, 2026 update added 80 procedure codes and deleted two. Plan for a second PCS cutover in the spring rather than treating October as the whole year's work.

The MS-DRG grouper moves to version 44 for FY2027. Version 43.1 was the April 2026 grouper.

One operational consequence sits under all of this. A claim is grouped on discharge date for inpatient and on date of service for outpatient, which means late September encounters billed in October still code to FY2026. Any system that swaps code sets on a calendar trigger rather than on the encounter date will misgroup that tail.

The additions worth building edits around

Circulatory system

Chapter 9 carries one of this year's larger expansions, with added detail for cardiomyopathies and a set of genetic and arrhythmia-related cardiac conditions. For inpatient teams this is a CC and MCC capture question before it is a documentation question, so it belongs on the FY2027 CDI education list rather than sitting in a coder-only briefing.

Endocrine

Two new codes, E89.830 and E89.838, were created to track hypoglycemia occurring after bariatric surgery and after other surgical procedures. Postsurgical hypoglycemia previously had no discrete reporting path. Bariatric programs and endocrinology services are the places to check whether documentation currently supports the distinction.

Body mass index

Z68.18 covers a BMI of 18.4 or less in adults. Z68.19 covers 18.5 through 19.9. Both fill in the low end of the Z68 range, which until now had far more granularity at the high end than the low end.

This is a malnutrition and frailty documentation change more than a BMI change. Severe malnutrition remains a clinician's diagnosis, not a coder's inference from a BMI value, and the FY2027 additions do not alter that. What they do is give the chart a place to record the number precisely enough to support the clinical picture.

History and exposure Z codes

Z86.17 reports a personal history of Clostridioides difficile infection. Z84.A reports a family history of exposure to diethylstilbestrol, with an instructional note under it setting out when the code applies.

The FY2027 file also adds exposure-history codes covering military and environmental exposures, and a block of codes addressing gender transition history. [VERIFY: exact code ranges and descriptors for the exposure and transition-history blocks against the 2027 Addendum before publish. See fact-check item 6.]

Neoplasm site specificity

Chapter 2 adds codes identifying specific anatomical sites for secondary neoplasms of the larynx and pharynx. Both the primary and the secondary site now need to be documented clearly enough to distinguish them, which is a familiar ask that this change makes materially harder to work around.

The changes that aren't new codes

This is the section most FY2027 summaries skip, and it is where the operational risk actually sits.

D05 moves from an Excludes1 to an Excludes2 note. Under the Official Guidelines, an Excludes1 note means two conditions are mutually exclusive and must never be reported together for the same encounter. An Excludes2 note means the excluded condition is not part of the code's definition, so both can be present and both can be reported. Carcinoma in situ of the breast can now be reported alongside the previously excluded condition where documentation supports it.

If you run a hard edit that blocks that pairing, it is now blocking a valid claim. That edit needs to be found and retired.

Two index entries reroute to different chapters. A search for polyp of the cecum previously landed on a benign neoplasm code in Chapter 2. For FY2027 the index directs it to a colon polyp code in Chapter 11. De Morgan's spots reclassify similarly.

Acute confusion gets a default. New index terms establish R41.0 as the default code for a diagnosis of acute confusion. Subterms were also added to support reporting sinusitis of odontogenic origin.

Index reroutes are the quietest failure mode in an annual update. No code was added or deleted, so a diff of the code list shows nothing. The code that was correct last year is still valid this year, just no longer the right answer for that diagnostic phrase. Anything that learned the old mapping, whether that is a coder's habit, an encoder shortcut, or an automated model, will keep producing a code that passes every structural edit and is wrong.

Guideline changes for FY2027

The FY2027 updates to the ICD-10-CM Official Guidelines for Coding and Reporting are light. One new guideline was added, and four existing guidelines were reworded or expanded.

The hypertension guidance in Chapter 9 picked up a wording change. Guideline I.C.9.a.1 on hypertension with heart disease now specifies "one or more" conditions, clarifying assignment of a code from category I11.

Where to get the file. As of its most recent update, the CMS ICD-10 page still lists the FY2027 ICD-10-CM Coding Guidelines PDF as not yet available, while the FY2027 ICD-10-PCS guidelines are posted there. The CM guidelines are published by NCHS. If your team is waiting on the CMS page, check the CDC's ICD-10-CM site instead. [VERIFY: current availability status on both pages on the day of publish. This is the kind of detail that changes weekly and dates the page fastest.]

What an October 1 cutover asks of an automated coding system

Any system that assigns codes from clinical documentation, whether that is an encoder, a computer-assisted coding tool, or an autonomous coding platform, has the same four exposures at a fiscal year boundary.

Version awareness: The system has to hold FY2026 and FY2027 concurrently and select by encounter date, not by processing date. Charts coded in October for September discharges are the test case.

Deleted code handling: Thirty codes leave the set. A chart that would have received one of them needs a defined path to its replacement, and the conversion table is where that mapping lives.

Instructional note logic: Excludes1 and Excludes2 behaviour is usually implemented as rules rather than learned from text. Rule changes like the D05 revision have to be found and edited by hand.

Index-derived defaults: Where a system's mapping was trained or configured against last year's index, a reroute like the cecal polyp change produces a structurally valid, clinically wrong code. Structural validation will not catch it. Only a targeted audit will.

Ask your vendor which of these four it handles automatically, which require a configuration change on your side, and what its FY2027 cutover date is. A platform that codes emergency department, radiology or inpatient volume at scale will surface a version-boundary error faster than a human team will, in both directions.

Pre-October 1 readiness check

#	Task	Owner
1	Download the 2027 Addendum and conversion table and confirm counts against your internal summary	Coding compliance
2	Identify every hard edit affected by the D05 Excludes revision and retire or amend it	Revenue integrity
3	Confirm your encoder and coding platform cut over on encounter date, not processing date	HIM and IT
4	Map the 30 deleted codes to replacements and check historical claim volume against each	Coding compliance
5	Brief CDI on the Chapter 9 circulatory additions before October 1, not after	CDI lead
6	Run a targeted post-go-live audit on the index-reroute diagnoses, which structural edits will pass	Coding audit
7	Confirm your MS-DRG grouper is on version 44	IT and revenue integrity
8	Diary the ICD-10-PCS mid-year cycle for April 1, 2027	HIM

Frequently asked questions

When do the ICD-10-CM 2027 changes take effect?

October 1, 2026. They apply to discharges and patient encounters through September 30, 2027. ICD-10-PCS FY2027 codes apply to discharges from October 1, 2026 through March 31, 2027, with a mid-year update effective April 1, 2027.

How many new ICD-10-CM codes are there for FY2027?

190 new codes, with 30 deletions and four revisions. Published summaries vary, so confirm against the CMS 2027 Addendum if the figure needs to hold up in an audit.

Do I use FY2026 or FY2027 codes for a September discharge billed in October?

FY2026. Code assignment follows the discharge date for inpatient and the date of service for outpatient, not the date the chart was coded or billed.

Are the FY2027 ICD-10-CM guidelines published?

The guidelines are maintained by NCHS. Check the CDC ICD-10-CM page, since the CMS ICD-10 page has at times listed the CM guidelines as pending while the PCS guidelines were already posted.

What changed that isn't a new code?

The D05 Excludes1 to Excludes2 revision, two Alphabetic Index reclassifications that move diagnoses to different chapters, a new default code for acute confusion, and four reworded guidelines. These carry more operational risk than the additions because nothing in a code-list comparison flags them.

Sources

• CMS, ICD-10 code files and FY2027 releases: https://www.cms.gov/medicare/coding-billing/icd-10-codes
• CDC / NCHS, ICD-10-CM: https://www.cdc.gov/nchs/icd/icd-10-cm.htm
• 2027 Addendum, 2027 Conversion Table, 2027 POA Exempt Codes (CMS, ZIP files, linked from the page above)
• FY 2027 Official ICD-10-PCS Coding Guidelines (CMS, PDF)