Every year the list of diagnosis codes used for billing gets updated, and the new version takes effect October 1.
This year CMS added 190 codes, deleted 30, and revised four. The updated set applies to resident stays from October 1, 2026 through September 30, 2027.
It’s a smaller update than some past years. Several changes apply directly to nursing homes, and missing one of them can get your October claims rejected.
The Changes Most Likely to Come Up in Your Building
Two new codes for underweight residents.
Everything at the low end used to fall under a single code, Z68.1, for a BMI of 19.9 or less. That one code covered a resident at 19.5 and a resident at 16 the same way.
FY2027 splits it. Z68.18 is a BMI of 18.4 or lower. Z68.19 covers 18.5 to 19.9. The dividing line is 18.5, which is the clinical threshold for underweight. So the record can now distinguish a resident who is genuinely underweight from one sitting at the low end of normal. That helps with malnutrition and frailty documentation, and it strengthens the clinical picture behind things like fracture risk.
One thing to keep in mind: BMI codes are secondary codes. They get reported alongside a diagnosis like malnutrition or unintentional weight loss, never on their own. The BMI figure itself can come from a dietitian’s or nurse’s documentation, but the underlying condition has to be documented by the provider.
A code for history of C. diff.
Z86.17 is the new code for a resident who has had a Clostridioides difficile infection in the past. That history has always mattered for infection control and readmission risk. Now there’s a code for it.
More specificity in cardiac coding.
Dilated cardiomyopathy has been split into more detailed codes, and several rarer cardiac conditions gained specificity too.
New codes for low blood sugar after surgery.
E89.830 and E89.838 cover hypoglycemia following bariatric and other procedures.
The Deleted Codes Are Where the Money Is
Thirty codes stop being valid on October 1.
Why does that matter?
If a resident in your building today is coded with one of those thirty, and that code is still on the claim you submit for October, the claim can get rejected.
CMS publishes a file called the conversion table. It’s a simple list of every code going inactive next to the code that replaces it.
The fix is straightforward. Pull the diagnosis codes attached to your current residents. Check them against that list. Update the ones with inactive codes.
This is worth doing sooner rather than later. Correcting a code now is much easier than working a denial after the fact.
MDS Coordinators Should Watch for the PDPM Mapping Update
The new codes also feed into the PDPM ICD-10 mapping tables. Those tables are what turn a resident’s diagnosis into the HIPPS code that drives Medicare reimbursement.
CMS posts the updated mapping separately, after the final rule. It’s worth downloading the current version as soon as it’s available so reimbursement isn’t calculated off last year’s mapping.
A New Code is Only as Good as the Note Behind It
A more specific code needs a more specific note. If the chart says exactly what it said last year, the new code won’t hold up on review.
Two things worth doing before October 1.
First, confirm your systems are updated. Both your electronic health record and your billing software need the FY2027 code set loaded. Most vendors push this automatically, but not all of them do, and not always on time. Ask yours directly.
Second, train narrowly. Look at the residents you actually have and figure out which of the new codes apply. Nobody needs to learn all 190. Most will never come up in a nursing home.
Nursing home coders need the current ICD-10 manual and coding guidelines to bill accurately.
September Checklist
- Compare the diagnosis codes on your current residents against the CMS conversion table, and update anything that’s going inactive October 1
- Ask your EHR and billing vendors to confirm the FY2027 codes are loaded
- Download the updated PDPM mapping tables when CMS posts them
- Pick the handful of new codes that apply to your residents and train staff on the documentation they require
- Replace any coding manuals still dated 2026
- Watch your October claims for denials, and trace any you get back to the source before they pile up
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