What changes in home health coding on October 1, 2026

The FY2027 ICD-10-CM update takes effect October 1, 2026. The five changes most likely to touch a home health claim, the date rule for episodes that cross October 1, and what to check this week.

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Enzo Health Team

Enzo Health

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Read Time: 6 min read

Date: September 24, 2026

If your agency bills Medicare, your coders switch to a new set of diagnosis codes on October 1. It happens every year, and most of it never touches a home health claim. This year a few changes will, and one of them turns a code you probably use today into an invalid one.

The date rule matters more than the code list

The code year follows the claim, not the OASIS. Medicare's home health billing manual says the codes on a claim describe the patient as of the claim's From date, and the grouper that sets your payment reads the claim's codes, not the assessment. So an episode that starts September 28 is coded from the September book.

There is one catch. If the claim's Through date crosses an update and a code on that claim stops being valid, the manual says the code that is valid after the update goes on the claim. In plain words: an episode that runs across October 1 keeps its September codes unless one of them died on October 1. Then it needs the new one. This year one code a lot of agencies use is in that spot.

Five changes most likely to show up in a home health claim

Dilated cardiomyopathy: I42.0 no longer stands on its own. From October 1, I42.0 becomes a heading with three codes under it: I42.00 (dilated cardiomyopathy, unspecified), I42.01 (familial-genetic) and I42.09 (other). A claim that still carries I42.0 by itself is carrying an invalid code. If you have heart failure patients on service today, this is the one to check first, including episodes that cross October 1. The same thing happens to "other cardiomyopathies," I42.8, which gains I42.81 (arrhythmogenic) and I42.89 (other, not elsewhere classified).
Two new codes for a low BMI. Z68.19 covers a BMI of 18.5 to 19.9 and Z68.18 covers 18.4 or less. Your CHF, COPD, advanced cancer and liver patients are where these will show up, and only where the record supports the number.
Cancer that has spread now has its own site codes for the head and neck. C78.31 (larynx), C78.32 (pharynx) and C79.83 (oral cavity) are new. The rule that comes with them: when the visit is about treating the spread, the spread is what you code first, even though the original cancer is still there.
A history code for C. diff. Z86.17 is a personal history of Clostridioides difficile infection. It is for the patient who had it and no longer has it, which is a different patient from the one with an active infection, and now the code says so.
Plantar fasciitis needs a side. It moves out of the fibromatosis code (M72.2) into its own category, split by side: M67.A01 (right), M67.A02 (left) and M67.A09 (unspecified). Fibromatosis of the plantar fascia splits the same way, M72.20, M72.21 and M72.22. Your diabetic foot and wound care patients are where this lands.

The smaller changes your coders will meet

Genetic disorders get their own place. Chapter 17's title now reads "Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders," and its range grows to Q00 to QA1. A documented genetic disorder can be coded from this chapter on its own, it stays with the patient for life, and a condition that was corrected gets a history code instead. New hereditary and cancer-predisposition codes arrive with it (Q87.A and the QA1.7 series).

The "present on admission" exempt list changed 75 times. Sixty-two codes were added, twelve removed and one revised. That flag is a hospital's job, not yours, but your coders will see the list move in their reference tools, and one familiar code (Z87.890) came off the exempt list as it split into six more specific ones.

Four new poisoning and toxic-effect groups. Alkenes, cycloparaffins, hexamethylene diisocyanate and medetomidine each get a new category with four codes (accidental, intentional self-harm, assault, undetermined). You will rarely see them in home health.

Hypoglycemia after surgery splits in two. E89.830 after weight-loss surgery, E89.838 after any other procedure.

What to check before October 1

Your EHR or coding tool has the FY2027 set loaded, and it picks the code year from the claim's From date. Ask your vendor to show you, not tell you.
Every open episode that crosses October 1 with I42.0 on it. Pull the list this week. Each one needs I42.00, I42.01 or I42.09 before the claim goes out.
Active patients whose record documents a BMI under 20. Where the documentation supports it, Z68.18 or Z68.19 belongs on the claim from October 1.
Your coders and QA reviewers have read the new Chapter 17 rule. It is two sentences in the guidelines and it changes how a genetic disorder is sequenced.
If you outsource coding, ask the vendor when they switch and what they do with claims that cross the date. Get it in writing.
Run QA on the first week of October claims before they bill. The changeover is where rejections come from, and they are cheaper to catch before the claim leaves.

What the coding words mean

From date and Through date. The first and last day of the period a claim covers. The From date sets which code book applies.

Principal diagnosis. The main reason for the plan of care, listed first on the claim. It drives your payment group.

Present on admission (POA). A flag hospitals put on a diagnosis to say it existed before the stay. Some codes are exempt from it. Agencies do not report it, but the exempt list ships with the code set.

NOS. "Not otherwise specified," which the guidelines define as the equivalent of unspecified.

Laterality. Whether the code says right, left or unspecified. More codes require it every year.

7th character. An extra digit some codes need for detail like which visit this is. A code that needs one and lacks it is invalid.

Excludes1 and Excludes2. Excludes1 means two conditions are never coded together. Excludes2 means the patient can have both, and both can go on the claim.

Where Enzo fits

Enzo's QA reviews the chart against the current ICD-10 rules before anything bills, so a code that stopped being valid on October 1 gets caught before the claim leaves, and your coder approves the fix instead of hunting for it. The changeover happens in the system, not on a sticky note above the monitor.