Every October 1, the ICD-10 code sets turn over, and every year some organizations find out weeks later that a piece of their build did not. The FY2027 update went live on October 1, 2026. By now the first claims carrying new codes have gone out, and the first denials and edit failures tied to the update are starting to come back. That makes late October the right time for a structured validation pass, not just a go-live checklist.

What changed on October 1

The FY2027 ICD-10-CM diagnosis code set adds 190 codes, deletes 30 and revises 4, according to the CMS files as summarized by ACDIS. These codes apply to patient encounters and discharges from October 1, 2026 through September 30, 2027. The largest single block is 33 new codes in category O31.4 for continuing pregnancy after vanishing twin syndrome. Other additions include 17 codes for toxic effects of cycloparaffins (T52.82), new secondary malignant neoplasm codes, a new pelvic disease category (K6A), odontogenic sinusitis (J34.83), plantar fasciitis (M67.A) and new BMI codes (Z68.18, Z68.19). The sternoclavicular sprain codes at S23.420 were deleted.

The FY2027 ICD-10-PCS procedure code set adds 101 codes, 50 of them in Section X (New Technology) across 13 tables, deletes 38 and revises 3, effective for discharges from October 1, 2026 through March 31, 2027. That end date matters: PCS now routinely receives an April 1 update, so procedure code tables need to be ready to change again mid-year.

The official files, addenda and guidelines are posted on the CMS ICD-10 page and, for diagnosis codes, through the CDC’s National Center for Health Statistics. There is no grace period: claims for dates of service or discharge on or after October 1 must carry valid FY2027 codes.

Validation checklist: the EHR build

Code tables and terminology content

  • Confirm the FY2027 ICD-10-CM and ICD-10-PCS tables loaded in production, not only in test. Spot-check a sample of new codes, including at least one from O31.4, K6A and Section X.
  • Confirm deleted codes are inactive for dates of service on or after October 1 but still valid for earlier encounters. Late charges and corrected claims for September discharges must still accept FY2026 codes.
  • Check revised code descriptions display correctly in problem lists, diagnosis pickers and printed documents.
  • If you license a clinical terminology layer that maps interface terms to ICD-10-CM, verify the vendor’s October content release is applied and that new mappings resolve.
  • Search for clinical terms tied to new codes, such as plantar fasciitis or odontogenic sinusitis, and confirm the picker surfaces the new, more specific code.
  • Run a report of active problem list entries still pointing to deleted codes. Problem lists are long-lived, and a deleted code on an active problem can carry into encounter diagnoses and claims.

Order sets, preference lists and favorites

  • Review physician preference lists, specialty favorites and order set diagnosis associations for deleted codes. These are frequently built at the department or user level and are easy to miss in a central update.
  • Check medical necessity diagnosis associations on lab and imaging orders. A deleted code here can block an order or trigger an unnecessary Advance Beneficiary Notice.

Clinical decision support and registries

  • Review CDS rules, health maintenance topics and registry inclusion criteria that use code-based value sets. New codes may need to be added to existing groupers. For example, a pelvic abscess now has its own category, which affects any infection-related registry logic.
  • Confirm quality measure value sets in the EHR match the versions used for the measurement period. Value sets for electronic clinical quality measures follow their own release cycle and may not include new ICD-10 codes until later.

Validation checklist: revenue cycle and claims

Charge capture and coding workflow

  • Confirm the encoder and computer-assisted coding tools are on their FY2027 content and the MS-DRG grouper version that took effect October 1.
  • Pull a sample of inpatient discharges since October 1 that used new PCS codes, especially Section X, and verify they grouped as expected. New technology codes often carry add-on payment implications, so an unexpected grouping deserves follow-up.

Claim scrubber and payer edits

  • Verify claim scrubber edits were updated for the new code set. Look for spikes in invalid-code or code-validity edits on claims dated October 1 or later.
  • Check that edits handle the date-of-service boundary correctly. A common failure is a scrubber rejecting a valid FY2026 code on a late charge for a September encounter.
  • Review National and Local Coverage Determination edits. Coverage determinations list covered diagnosis codes, and those lists are updated on their own schedule. A new, more specific code may not yet appear as covered.

Denial monitoring

  • Build a short-term report of denials since October 1 with reason codes related to invalid diagnosis or procedure codes, and break it out by payer. Commercial payers do not always update their systems on the same day as CMS.
  • Track how many denials trace to build issues inside your own systems versus payer-side lag. The fixes are different.

Validation checklist: data and reporting

  • Update data warehouse dimension tables for the new codes and descriptions. Reports that join encounter diagnoses to a static code table will show blanks or “unknown” for new codes until this is done.
  • Review any analytic groupings, such as condition categories, service lines or risk adjustment mappings, that rely on code ranges. New codes inside an existing range may be grouped automatically, while new categories like K6A will not be picked up by range logic written before they existed.
  • Check outbound feeds to registries, public health agencies and payers that validate codes against their own tables. Rejections there often come back as interface errors rather than claim denials.

Getting ready for April

ICD-10-PCS, and in some years ICD-10-CM, can now change on April 1. Treat the October validation as the template for a smaller spring cycle: keep the test scripts, the list of build locations that hold codes, and the denial report. The organizations that handle the October turnover smoothly are generally the ones that know exactly where in their EHR and revenue cycle systems a diagnosis or procedure code is stored, and they check each of those places every time the code set changes.