Exclusion notes are among the most misunderstood conventions in ICD-10-CM — and the April 1, 2026 update quietly changed several of them in ways that affect everyday code assignment. If you skimmed past the mid-year update because it contained no new diagnosis codes, it’s worth a second look.
A quick refresher
Excludes1 means “not coded here — ever.” The two conditions are mutually exclusive; you should never report both codes together (with narrow exceptions when the conditions are truly unrelated).
Excludes2 means “not included here, but may coexist.” The excluded condition isn’t part of the code you’re looking at, but a patient can legitimately have both, so both codes may be reported together when documentation supports it.
The distinction sounds academic until a claim bounces or an auditor flags a code pair you reported — or didn’t report — incorrectly.
What changed in April 2026
The April update revised several Excludes1 notes to Excludes2, acknowledging that certain condition pairs can genuinely coexist. Two examples with real clinical impact:
Multiple sclerosis. Relapsing-remitting MS (G35.A) previously carried an Excludes1 note against G37.9 (demyelinating disease of central nervous system, unspecified). That’s now an Excludes2 note, so both may be coded together when clinically appropriate.
Long-term opioid therapy and methadone. Z79.891 (long-term current use of opiate analgesics) previously excluded the methadone use codes F11.9 and F11.2 outright. Those exclusions became Excludes2 notes, recognizing that a patient can be on long-term opioid therapy and also have documented methadone use or treatment.
The update also replaced some “Code First” instructions with “Code Also” notes — a meaningful shift, since “Code First” mandates sequencing while “Code Also” leaves sequencing to the coder’s judgment based on the encounter.
Why mid-year updates deserve a standing calendar reminder
CMS now updates ICD-10-CM twice a year: October 1 and April 1. The April cycles tend to be small — often no new codes at all — which makes them easy to ignore. But as this cycle shows, a changed exclusion note or instructional note can flip a code pair from “never together” to “report both,” and that directly affects reimbursement, risk adjustment, and audit exposure.
Action items
- Download the April addenda files from the CMS ICD-10 page and keep them with your coding references.
- Check whether your encoder and CDI software picked up the revised notes — vendor update lags are common on mid-year cycles.
- Re-educate on any condition pairs your organization codes frequently that were affected by the Excludes1-to-Excludes2 revisions.
The coders who read the addenda are the ones who catch revenue and compliance issues the software misses.
Always consult the current official ICD-10-CM tabular list and guidelines when assigning codes.
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Originally Published On: Medical Coding News
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