The fiscal year 2026 ICD-10-CM files are out. CMS posted them on June 6, and the count is 487 new diagnosis codes, 28 deletions and 38 revised descriptions, all effective for dates of service on or after October 1, 2025. It is a mid-sized update by recent standards, after the 395 additions of fiscal year 2024 and a smaller set in fiscal year 2025, and it lands on a Wednesday, which means the first full week of October will show you exactly which systems, favorites lists and payer edits were not ready.
We have been through enough October transitions to know the pattern. The codes are loaded in September. The rejection report on October 2 shows "invalid diagnosis code" for a batch of claims, because a deleted code was still on a provider's favorites list, or a new code was used for a September date of service. Then a payer that loaded the files late denies the new codes for two weeks. None of it is serious and all of it is avoidable if the preparation starts now rather than in the last week of September.
Key takeaways
- 487 new codes, 28 deletions and 38 revisions take effect October 1, 2025, by date of service, with no grace period from Medicare.
- The changes most likely to reach an office claim: E11.A for type 2 diabetes in remission, multiple sclerosis subtypes under G35, 16 new abdominal and pelvic pain and tenderness codes under R10, cannabis hyperemesis syndrome R11.16, and food allergy codes that distinguish tolerance to baked egg and milk.
- The 28 deletions are the immediate risk: any of them still on a favorites list, superbill or order set on October 1 produces a rejection.
- June is for reading and listing, July for vendor confirmation, August for fixing pick lists, September for provider education, October for watching the rejection report daily.
- Add the codes your practice will actually report to the pick lists, not all 487.
What is in the update for an office-based practice
The full addenda run to hundreds of pages, and much of the volume is in injury, external cause and highly specialized codes. The changes most likely to reach an ambulatory claim are these.
| Area | New codes (examples) | Who will use them |
|---|---|---|
| Diabetes | E11.A, type 2 diabetes mellitus without complications, in remission | Primary care, endocrinology; a documentation question for providers about what "remission" means in the note |
| Multiple sclerosis | G35 becomes a parent code with subtypes for relapsing-remitting, primary progressive and other phenotypes | Neurology |
| Abdominal and pelvic pain | 16 new R10 codes for abdominal, pelvic and perineal pain and tenderness by site; R10.2 becomes a parent code | Primary care, urgent care, gastroenterology, emergency |
| Nausea and vomiting | R11.16, cannabis hyperemesis syndrome | Primary care, urgent care, gastroenterology, emergency |
| Food allergy | T78.07 and T78.08 series for reactions to milk and egg with tolerance to baked forms; Z91.011 and Z91.012 become parent codes for milk and egg allergy status | Allergy, pediatrics |
| Breast cancer | C50.A series, inflammatory breast cancer by laterality | Oncology, breast surgery |
| Kidney disease | N07.B, APOL1-mediated kidney disease; new codes for immune complex membranoproliferative glomerulonephritis under N00 and N04 | Nephrology, primary care |
| Social determinants | Z59.86 (financial insecurity) expands into child codes; Z77.3 series for exposure to war or conflict zones | Any practice capturing SDOH; relevant to quality programs |
| Genetic susceptibility | Z15.06 series, genetic susceptibility to malignant neoplasms of the digestive system | Oncology, genetics, gastroenterology, primary care |
| Toxicity | New codes for toxic effect of xylazine under T65 | Emergency, addiction medicine |
The deletions matter as much as the additions. Twenty-eight codes disappear on October 1, and any of them that sits on a favorites list, a superbill, an order set or a payer's medical policy will cause a rejection or a denial. Several of the deletions are codes that became parent codes this year (R10.2, Z91.011, Z91.012 and G35 among them), which means a code your providers have used for years now needs a fifth or sixth character. The conversion table in the CMS files maps each deleted code to its replacements.
E11.A deserves a conversation, not just a load
E11.A is the code providers will ask about. It is meant for patients whose type 2 diabetes has been in remission, which the specialty societies define as normal glucose levels sustained for at least three months without glucose-lowering medication, and it applies only when the provider documents remission and there are no current diabetic complications. That is a clinical judgment the provider has to write down; a coder cannot infer it from an A1c. It also has consequences: a patient coded E11.A instead of E11.9 may drop out of diabetes quality measure denominators and risk adjustment categories, which is correct if the patient is in remission and a problem if the code was picked because it sounded good. Ten minutes at a provider meeting in September on what the note needs to say is the whole preparation.
The June-to-October plan
- June: download and read. Someone on the coding side downloads the addenda and the conversion table from the CMS ICD-10 page and reads the sections relevant to the practice's specialties. Two hours. Make a list of the new codes the practice will actually use and the deleted codes it currently uses.
- July: ask the vendors. Ask the EHR, practice management and clearinghouse vendors, in writing, when they will load the FY 2026 files and whether the load is automatic. Ask the same of any encoder or coding assistance tool. Record the answers.
- August: fix the lists. Update provider favorites, superbills and order sets so deleted codes are replaced and new codes are available. Do this in a test environment if the system allows and schedule the production change for the last week of September, because the new codes must not be used before October 1.
- September: educate and watch the guidelines. The Official Guidelines for FY 2026 are usually posted after the code files; read the changes and brief providers on the documentation the new codes need. Ten minutes at a provider meeting on E11.A and the pain codes covers most primary care practices.
- October 1 to 15: run the rejection report daily. Any diagnosis-related rejection gets fixed the same day. Watch each top payer for denials of the new codes in the first two weeks; a payer that has not loaded the files will deny them as invalid, and a call to provider relations with the CMS release as evidence usually resolves it.
The date of service rule
ICD-10-CM codes apply by date of service for professional claims, not by claim date. A visit on September 30 uses the FY 2025 code set even if the claim is submitted in October; a visit on October 1 uses FY 2026. There is no grace period from Medicare and most commercial payers follow suit. This is the single most common cause of first-week rejections, and it is a system setting: the practice management system must select the code set by date of service, and a coder must not be able to assign a new code to a September encounter.
A worked example of how it goes wrong. A gastroenterology practice loads the FY 2026 files on September 22 because the vendor's update window fell that week. A provider sees a patient on September 26 with right lower quadrant tenderness and picks one of the new R10 tenderness codes from the updated list. The claim goes out on October 3 and rejects at the clearinghouse: code not valid for date of service. Multiply by the 40 encounters coded from the new list between September 22 and September 30 and the practice has a batch of rejections to recode by hand in the first week of October, all because the production load happened a week early. Load in test in August; load in production on September 30 after the last claim of the day, or October 1 before the first.
Mistakes we see every October
Loading the files late because the vendor said "automatic" and it wasn't. Leaving deleted codes on favorites lists because nobody owns the lists. Educating coders but not providers, so the notes do not contain the detail the new codes require and the coder defaults to the unspecified code. And treating the update as a coding department event when the front desk (order entry), the providers (documentation) and the billing team (rejections) all have a part.
One more, which is a matter of opinion: practices that add every new code to the pick lists "just in case" end up with lists nobody can use. Add what the practice will actually report. The encoder has the rest.
Revelrex covers each annual update in the live RCM training courses, and medical coding clients receive the specialty-specific code list and the favorites review as part of the service.
Questions we hear
Do we need to update our fee schedules or CPT codes at the same time?
No. CPT and HCPCS updates take effect January 1 (with some quarterly HCPCS changes). October 1 is diagnosis codes and the inpatient procedure code set, ICD-10-PCS, which office practices do not use.
Will payers deny E11.A because it is new?
Some may in the first weeks if their systems lag. Check each payer's medical policies for diabetes-related services and confirm they recognize the new code. Keep the CMS release notice handy for the appeal.
Where do the guidelines fit in?
The Official Guidelines for Coding and Reporting are updated for each fiscal year and often posted a few weeks after the code files. Read the change summary at the front of the document; it is usually short and it is where instructions about sequencing and new chapter notes live.
What to do this month
- Download the FY 2026 addenda and conversion table and identify the codes that touch your specialties.
- List every deleted code currently on a favorites list or superbill, with its replacement from the conversion table.
- Send the vendor question in writing to the EHR, practice management, clearinghouse and encoder vendors, and calendar the answers.
- Book fifteen minutes at a September provider meeting for the documentation changes, starting with E11.A.
- Decide who runs the rejection report daily from October 1 to 15 and who fixes what it finds.
