The FY2027 ICD-10-CM code set takes effect on October 1, 2026. It adds 238 new diagnosis codes, deletes 21, and turns 15 codes that were billable yesterday into non-billable headers. The deletions and the demotions are where claims fail, because a code that stops being valid stops being payable on the first date of service it no longer covers. Practices that handle this well run the same process every summer, months before the effective date.
What this covers
- The FY2027 ICD-10-CM set applies to encounters and discharges from October 1, 2026 through September 30, 2027.
- 238 new codes, 21 deletions, and 15 codes that stop being billable, counted from the CMS FY2027 order file.
- Deletions and demotions break claims. New codes are optional until the record supports them.
- Pull your own diagnosis frequency report first, so the review has a priority order.
- Your EHR vendor, clearinghouse and payers each have a separate load date. Confirm all three in writing.
A new code is optional until the record supports it. A deleted code is invalid from the first date of service it no longer covers.Why the deletion list, not the addition list, drives October denials
The size of the update is not the point. FY2027 is a smaller cycle than FY2026, and a small cycle still breaks claims when a high-volume code is the one that changed. Cardiology and podiatry carry that risk this year: I42.0 and M72.2 both stop being billable on October 1, 2026, and both sit in the favorites lists of practices that bill them every day.
What follows is the working method: what changed, how to find which changes touch your specialty, and a calendar that puts the work in the summer.
What changes on October 1, 2026
The FY2027 ICD-10-CM files were posted in June 2026 by CDC’s National Center for Health Statistics, which maintains the diagnosis classification, and are linked from the CMS ICD-10 page. CMS instructs you to use those files for discharges and patient encounters occurring from October 1, 2026 through September 30, 2027. The code set follows the date of service, not the date you submit the claim and not the date the note was written.
Two things do not move with the diagnosis set. ICD-10-PCS procedure codes for inpatient discharges run October 1, 2026 through March 31, 2027, then take a mid-year update on April 1, 2027. And the administrative machinery has its own dates: CMS issued change request 14503 on June 16, 2026 to give Medicare contractors the October 2026 (2027 file) ICD-10-CM update, with an implementation date of October 5, 2026.
The Medicare contractor implementation date in CR 14503 is October 5, 2026, four days after the codes become effective. Watch first-pass rejections closely on claims with October 1 through October 4 dates of service, and check whether your MAC posted its own bulletin.
Four files do the work: the code descriptions in tabular order, the addendum showing every line added, deleted or revised, the conversion table that maps each retired code to its replacement, and the FY2027 Official Guidelines for Coding and Reporting. All four are on the CMS page, and the diagnosis files and guidelines are also published by NCHS on the CDC site.
The four kinds of annual change
Not every change is a new code, and the four categories fail in different places. A billing manager who reads only the new-code list has read the least dangerous part of the update.
| Change type | What it does | Where it breaks |
|---|---|---|
| New codes | Adds specificity, often splitting one code into a category with children | Templates and favorites with no entry for the new code, so coders default to unspecified |
| Deleted codes | Removes a code from the valid set on the effective date | Any claim carrying that code on a date of service on or after October 1 is rejected |
| Billable to header | The code still exists but stops being a codeable option | Encoder and scrubber edits fire, so the claim never leaves the system |
| Description and note changes | Rewrites Excludes1, Excludes2, Code Also and index entries without changing the number | Coding logic that was built as a rule rather than read from the text |
The FY2027 files produced 238 additions, 21 deletions, and 15 codes that moved from billable to header status. AAPC’s analysis of the same files reports four revised code descriptions. For a billing manager, the number that matters is 36: the codes that either leave the set or stop being codeable.
Published totals for this update differ, because some summaries count only billable additions and some count every new entry including non-billable headers. Count from the source. The FY2027 order file holds 238 entries that were not in the FY2026 order file, 190 of them billable, and 21 entries that are gone.
Where the FY2027 codes landed
New codes cluster by chapter, so start with the chapters your practice codes in. The specialty pages list the diagnosis families each practice type lives in.
| Chapter | New codes | Examples |
|---|---|---|
| 19 Injury and poisoning | 85 | T52.8X organic solvents split into alkenes, cycloparaffins and other solvents |
| 15 Pregnancy and childbirth | 56 | Interstitial, cesarean scar, cervical and cornual ectopic pregnancy; continued pregnancy after vanishing twin |
| 13 Musculoskeletal | 33 | M67.A plantar fasciitis by laterality; M86.8X osteomyelitis with a site character |
| 21 Factors influencing health | 17 | Z68.18 and Z68.19 for adult BMI; Z77.32 burn pits, Z77.33 Agent Orange, Z77.4- blast overpressure |
| 9 Circulatory | 9 | I42.00, I42.01, I42.09, I42.81, I42.89, I47.22, I49.81, I49.82 |
| 17 Congenital and genetic | 9 | Q00-QA1 expansion for genetic disorders |
Cardiology carries the change most likely to generate denials. I42.0 becomes a header on October 1, 2026, and you code to I42.00 for unspecified, I42.01 for familial-genetic, or I42.09 for other dilated cardiomyopathy. I42.8 splits into I42.81 and I42.89. I49.8 becomes a header with I49.81 for Brugada syndrome and I49.82 for ventricular bigeminy underneath it.
Musculoskeletal and podiatry work gains laterality it never had. Plantar fasciitis moves from M72.2 to M67.A01 for the right foot, M67.A02 for the left foot, and M67.A09 when no side is documented. The M86.8X osteomyelitis codes gain a character for right, left or unspecified at eight sites. The sternoclavicular sprain family under S23.420 is deleted outright.
Pregnancy coding gains 56 codes, mostly site and trimester detail for ectopic pregnancy and vanishing twin syndrome. Chapter 21 gains 17 Z codes covering BMI under 19.9, environmental and military exposures, and gender transition history. If your practice documents any of those, the pick list changes even though the clinical work does not.
Map the changes to your most-billed diagnoses
Reading the addendum from the top is the wrong order. Start with what you bill, then read only the part of the addendum that touches it.
- Run a diagnosis frequency report for the last 12 months. Export the code, the description, the claim count, total allowed amount, and the number of distinct rendering providers.
- Rank by claim count and by allowed amount separately. A code can be low volume and high value, or the reverse.
- Take the top 50 by claim count and the top 25 by allowed amount, and merge the two lists.
- Match that list against the FY2027 deleted list, the demoted header list, and the addendum entries for those code families.
- For every match, write down the replacement code and the documentation the replacement requires.
- Repeat against the top 20 codes for each payer that returns coding edits on remittance.
Diagnosis frequency has to come from your own system. CMS publishes a physician and practitioner utilization file, but it is keyed to HCPCS procedure codes, so it will not tell you which diagnoses a specialty bills most. Your practice management system, your clearinghouse reports, or a payer’s remittance data will.
The output of this exercise is one page: code, current description, status on October 1, replacement code, and the documentation gap the replacement exposes. Everything downstream, from template edits to coder education to provider queries, reads off that page. Our medical coding and billing team builds it the same way for every specialty it works with.
What has to land before October 1
Your own code list is the smallest part of the work. Five other systems have to be ready, each with its own date.
| Dependency | What you need from them | When |
|---|---|---|
| EHR or practice management vendor | The date the FY2027 code set loads into your production instance, in writing | Before your internal go-live, not on October 1 |
| Clearinghouse | Confirmation that the new codes pass front-end edits | Before the first October claim |
| Medicare | CR 14503 implementation for your MAC | October 5, 2026 |
| State Medicaid and commercial payers | Which of them hold their own diagnosis edit lists, and their effective date | 30 days before the cutover |
| Encoder or computer-assisted coding | Rule updates for the changed Excludes and Code Also notes | With the code load |
Ask for two dates: the date the new set is available in your production instance, and the date your test environment has it. Templates, favorites and superbills have to be edited against the new set before coders touch it, so a vendor date that lands on October 1 gives you no time to prepare.
Then sweep every place a code is stored, because a code lives in more places than most teams expect.
- Favorites and quick-pick lists in the EHR and the practice management system
- Encounter forms, order sets and superbills
- Macros and dictation templates
- Printed cheat sheets at the front desk and in exam rooms
- Open plans of care that run past October 1
Guideline changes worth an hour of coder time
The FY2027 Official Guidelines for Coding and Reporting are published, and I compared them against the FY2026 version. Three changes are worth reading in full.
- Hypertension with heart disease. Guideline I.C.9.a.1 now reads one or more heart conditions classified to I50.- and the listed I51 codes, where the prior version read heart conditions. The instruction to assign a code from category I11 with an additional code from I50 or I51 is unchanged, but the plural wording settles how to treat a single documented condition.
- Chapter 17 now covers genetic disorders. The chapter heading and the coding instructions were expanded from congenital malformations, deformations and chromosomal abnormalities to include genetic disorders in categories Q00-QA1.
- Diethylstilbestrol exposure. The guidelines add a note for Z84.A, family history of exposure to DES, and a companion note for Z91.B, personal risk factor of exposure to DES, which is used when the patient was directly exposed in utero. Both codes existed before FY2027. The notes are new.
The remaining FY2027 guideline edits are wording, heading and cross-reference changes. That does not make them free. Any coding rule your team built around a specific sentence has to be re-read, because a reworded guideline can change a sequencing decision without changing a single code.
A working timeline that starts well before October
The annual update is the same job every year with different codes. Put it on the calendar as a sequence and the last week of September stops being a crisis.
Download the FY2027 order file, the addendum and the conversion table. Count additions, deletions and demotions yourself, so nobody argues about totals in September.
Export your top diagnosis codes by volume and by allowed amount and cross-match them against the deleted list, the demoted header list and the addendum entries for those families.
Update favorites, encounter forms, superbills, macros and printed references in a test environment. Do not delete a code that is still valid for September dates of service.
Get the production load date from your EHR and practice management vendor, and a pass or fail answer from the clearinghouse.
Run coder education on the changes that touch your specialty and build a documentation query list for the new specificity, such as the side of the foot, the sinus involved, or the type of cardiomyopathy.
Load the new set in production, run a sample of recent charts through it, and confirm both code sets are available for encounters that straddle the cutover.
Track the first-pass rejection rate daily for two weeks. A cluster of invalid-code rejections means a stored code was missed.
Reading this in the last days before October 1, cut the list to three items: the deleted codes, the demoted headers, and the vendor load date. Everything else can be caught in the first weeks of October without a claim denial.
FY2027 ICD-10-CM questions
October 1, 2026. The FY2027 diagnosis set applies to patient encounters and discharges occurring from October 1, 2026 through September 30, 2027. ICD-10-PCS procedure codes for inpatient discharges run October 1, 2026 through March 31, 2027, with a mid-year update on April 1, 2027. The code set follows the date of service, so a September encounter still uses the FY2026 set even when you bill it in October.
The FY2027 order file contains 238 codes that were not in the FY2026 order file, 190 of them billable, and 21 codes that are gone. Another 15 codes stop being billable and become non-billable headers, including I42.0 and M72.2. AAPC’s analysis of the same files reports four revised code descriptions. Published totals vary because some summaries count only billable additions.
The claim is rejected as an invalid diagnosis. There is no grace period and no first-pass tolerance. The conversion table in the FY2027 files maps each deleted code to its replacement, so the fix is mechanical once you know which of your codes is on the list. The real cost is rework, because the encounter may need a documentation query before it can be rebilled.
No. I42.0 dilated cardiomyopathy becomes a non-billable header on October 1, 2026, and you code to I42.00 for unspecified, I42.01 for familial-genetic, or I42.09 for other dilated cardiomyopathy. I42.8 splits the same way into I42.81 and I42.89, and I49.8 becomes a header with I49.81 for Brugada syndrome and I49.82 for ventricular bigeminy beneath it.
Only when the record supports them. A new code is not required for a condition you can still describe with an existing valid code, and new codes are not applied retroactively to earlier dates of service. The exception is a code that replaced a deleted one, where the replacement is mandatory from the effective date. Check the conversion table rather than a favorite list.
The CMS ICD-10 page hosts the 2027 code descriptions in tabular order, the addendum, the conversion table, POA exempt codes, and the FY2027 Official Guidelines for Coding and Reporting. CDC’s National Center for Health Statistics publishes the same diagnosis files, including the guidelines PDF and the table and index files. Both pages are updated and both are free.
The bottom line
The FY2027 update is small on paper and still expensive when a favorite code goes invalid unnoticed. The work is a frequency report, a crosswalk, and three vendor confirmations. Put it in the calendar for next summer, because the FY2028 files will arrive the same way.
Are your top 50 diagnosis codes still valid on October 1, 2026?
Our RCM team runs the FY2027 crosswalk against your own billing data, updates the templates and favorites lists where we control them, and reports which codes changed and what documentation the replacements require. Send us a diagnosis frequency export and we will show you the exposure before the first October claim goes out.
Request a free ICD-10 readiness auditThis article describes the FY2027 ICD-10-CM files published by CMS and CDC as of late September 2026 and is general guidance, not a coding determination for a specific claim.
