The ICD-10 code sets are revised once a year. Changes take effect for discharges and encounters on or after October 1, and there is no grace period. A claim is coded according to the code set in effect on the date of service, not the date it is submitted.
What changes
- New codes - usually additional specificity within an existing category, sometimes an entirely new concept.
- Deleted codes - often because a code was split into more specific children.
- Revised descriptions - the code stays, its wording changes. These are easy to miss and can change which code is correct.
- Changed instructional notes - excludes notes, code first instructions and sequencing rules are all revised.
- Guideline changes - the official guidelines are updated alongside the codes.
The last two are the ones that catch experienced coders, because nothing about the code number itself looks different.
Date of service governs
For inpatient stays the relevant date is the discharge date, not the admission date. A patient admitted in late September and discharged in October is coded under the new set for the entire stay. Stays that straddle the boundary are where the mistakes cluster.
Why URLs on this site do not change
A code page here keeps the same address across annual updates. Many reference sites put the year in the URL, which means every link, bookmark and citation breaks each October and the page starts over with no history.
We took the opposite approach deliberately: the content updates, the address does not. A page you cite this year still resolves next year.
A workable preparation routine
- Summer - the files are published well ahead of the effective date. Review new and deleted codes in your highest-volume specialties first; that is where the impact concentrates.
- Before October 1 - update encoder software, superbills, cheat sheets, EHR pick-lists and any internal documentation. Stale pick-lists containing deleted codes are a classic source of October rejections.
- Read the deletions carefully. A deleted code usually means a replacement exists with more required detail - which may mean the documentation now needs to capture something it did not before.
- Brief the clinicians. Where new specificity requires new detail in the record, coders cannot solve it alone.
- Watch October denials. A cluster in the first weeks usually points at one stale list rather than many separate errors.
Checking this year's changes
The 2027 changes page lists the ICD-10-CM and ICD-10-PCS codes added and deleted in the current cycle. The 2027 set is effective for dates of service on or after October 1, 2026.
As always, the official CMS and NCHS publications govern - this site is a reference, and the source files are the authority.