CMS and the CDC released the fiscal year 2026 ICD-10-CM files in June. The update takes effect for dates of service on and after October 1, 2025, and it adds 487 new diagnosis codes, revises 38 and deletes 28. The largest blocks of additions are in Chapter 19, injuries and poisoning, which gains new contusion codes for the abdominal wall, groin and flank and new codes for anaphylaxis to specific foods, and Chapter 12, skin and subcutaneous tissue, where 116 new codes classify non-pressure chronic ulcers by site and depth. Chapter 18 adds sixteen R codes for abdominal, pelvic and perineal pain and tenderness. The guideline changes touch HIV coding, conditions involving multiple sites, and type 2 diabetes in remission.
None of this is dramatic. The update is smaller than several recent years. And yet every October we watch practices lose two to four weeks of clean claims to a code set change they knew about for months. The failure is never the coder. It is the favorites list in the EHR that still points at a deleted code, the order set that maps to a code that now needs a seventh character, and the payer that did not update its edits until mid-October.
Ninety days is enough time to do this properly. Here is how we lay it out.
Key takeaways
- The FY 2026 update is modest: 487 new codes, 38 revised and 28 deleted, effective for dates of service on and after October 1, 2025. The risk is in the systems, not the size.
- Run one report first: twelve months of billed diagnosis codes against the deleted and revised lists. The intersection is usually a handful of codes and that is where the money is.
- Favorites lists, order sets, superbills, interfaces and scrubber edits each need a named owner and a done-by date. The vendor table load is day one, not day ninety.
- Check your top five payers' medical policies for codes that drive coverage; a payer that lags the update will deny valid claims in October and you want to know that in September.
- Do not load the new tables early and do not use new codes before October 1. Date of service decides the code set, not the billing date.
Days 1 to 15: know what actually affects you
Download the FY 2026 addendum and conversion table from the CMS ICD-10 page. Then run one report: every ICD-10-CM code your practice billed in the last twelve months with a count. Match that list against the 28 deleted codes and the 38 revised codes. In most practices the intersection is a handful of codes, and that handful is where the money is.
Then look at the new codes by chapter for your specialty. An orthopedic or urgent care practice needs to read the Chapter 19 injury additions. A dermatology practice needs Chapter 12. A primary care practice should read the diabetes remission guidance and the new codes it will be asked for by quality programs. A practice that bills none of the affected chapters can shorten this plan considerably, but it still needs the system work below.
Days 16 to 45: fix the systems, not the people
Favorites, pick lists and templates
Every provider has a personal favorites list, and every deleted code that lives on one will be selected on October 1 and rejected at the clearinghouse. Export the favorites lists (your EHR vendor can usually do this), find the deleted codes, and replace them with the FY 2026 equivalents before the update loads. Do the same for shared pick lists, problem list templates and the diagnosis fields on order sets.
Charge capture and superbills
If any part of the practice still uses paper or PDF superbills, the diagnosis section needs a new version dated October 1. Print it in September but do not distribute it early. Using a new code before October 1 is as wrong as using a deleted one after.
Interfaces
Lab, imaging and referral interfaces carry diagnosis codes. Ask each connected vendor in writing when their FY 2026 tables load. The answers vary, and an interface that rejects a valid new code because the receiving system has not updated is a real October problem.
Claim scrubber edits
Your clearinghouse and any scrubber rules built in-house have date-effective tables. Confirm that the FY 2026 code set is scheduled for October 1, and check any custom edits that reference specific codes (for example, a rule requiring a laterality character on certain codes) for the new additions.
Days 46 to 75: payers and training
Payers publish their own code set updates, and some lag. Check the medical policy pages of your top five payers for FY 2026 policy updates, particularly where a diagnosis code drives coverage: prior authorization lists, medical necessity edits for labs and imaging, and any policy that names ICD-10-CM codes explicitly. When a payer's policy still lists a code that will be deleted, the claim will deny after October 1 until the payer catches up, and knowing that in advance lets you plan the appeal rather than discover it.
Training belongs here, not in September. Two sessions are usually enough: one for providers on the guideline changes and the new codes in their specialty, and one for coders and billers on the deleted and revised codes and the payer policy findings. Keep provider training to 30 minutes and specific to their favorites list. General ICD-10 education in a code update meeting is where attention goes to die.
Days 76 to 90: dress rehearsal
In the last two weeks of September, run the twelve-month code report again and confirm every deleted code has a documented replacement. Load the new superbill. Confirm the EHR update is scheduled for the night of September 30 and that someone is checking the system on the morning of October 1. Set a daily rejection report review for the first ten business days of October, with one person assigned.
The table we use
| Item | Owner | Done by | Check |
|---|---|---|---|
| Twelve-month code usage vs. deleted and revised list | Coding lead | Day 15 | List of affected codes with replacements |
| Provider favorites and pick lists | EHR administrator | Day 45 | No deleted codes in any list |
| Order set and template diagnosis fields | EHR administrator | Day 45 | Mapped to FY 2026 codes |
| Interface vendor confirmations | Practice manager | Day 45 | Written load dates |
| Payer policy review, top five payers | Billing lead | Day 75 | Findings logged with expected denial risk |
| Provider and staff training | Coding lead | Day 75 | Attendance recorded |
| October 1 morning check and daily rejection review | Billing lead | Day 90 | Calendar entries for ten business days |
What a bad October costs
The two to four weeks of disruption we mentioned is not an abstraction. Take a practice that files 400 claims a week. If 4 percent of them carry a deleted or incomplete code in the first two weeks of October, that is 32 rejections. Each one takes a biller ten to fifteen minutes to find, correct and refile, so about seven hours of rework, and each corrected claim pays two to three weeks later than it would have. At an average $140 per claim, roughly $4,500 sits in rejected status for most of October. That is the mild version. The expensive version is the payer whose edits reject a valid new code for six weeks and the practice that does not notice because rejections are reviewed monthly. Ten business days of daily rejection review in October is the cheapest insurance in this plan.
Mistakes that cost money every year
Loading the update early. Some EHRs allow the new tables to be activated before October 1, and someone always does it, producing a week of claims with codes that do not yet exist. Forgetting the date of service rule: a September 29 visit billed on October 3 uses FY 2025 codes. Ignoring the seventh character on new injury codes; a rejection for an incomplete code is the most common October rejection we see. And assuming the coder will catch everything at the back end. The coder catches what reaches them; a provider who selects a deleted code from a favorites list and signs the note has created rework that a system fix would have prevented.
Questions we hear
Do we need to buy new code books?
The official code set, tables, index and guidelines are free on the CMS and CDC sites. Commercial books and encoder subscriptions are convenience, not requirement. What you need is the addendum and the conversion table, and those are free.
Our EHR vendor says the update is automatic. Are we done?
The table load is automatic. Your favorites lists, templates, order sets and superbills are not, and neither are your payers. The vendor update is day one of the plan, not day ninety.
Where does the CPT update fit?
The CPT 2026 code set is expected from the AMA in September and takes effect January 1, 2026. It gets its own 90-day plan starting in October. Our live RCM training courses cover both updates each year, and the same checklist works for both.
What to do this week
- Download the FY 2026 addendum, conversion table and guidelines from the CMS and CDC ICD-10 pages and save them where the coding lead and the EHR administrator can both reach them.
- Run the twelve-month diagnosis code usage report and match it against the 28 deleted and 38 revised codes. Write the replacement for each affected code next to it.
- Ask the EHR vendor, in writing, for the date the FY 2026 tables load and whether favorites lists can be exported and edited in bulk.
- Assign the owners in the table above and put the Day 15, Day 45, Day 75 and Day 90 dates on the practice calendar.
- Book the two training sessions for the Days 46 to 75 window now, while provider calendars still have room.
