GEMs and the ICD-10-CM Fiscal Year Update Cycle
How the ICD-10-CM fiscal-year update works (new, revised and deleted codes effective October 1), how proposals are made, and what the General Equivalence Mappings (GEMs) are and are not for.
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Short answer
ICD-10-CM is updated each fiscal year, with new, revised and deleted codes taking effect on October 1, and changes are proposed and discussed at the public ICD-10 Coordination and Maintenance Committee meetings. The General Equivalence Mappings (GEMs) are CMS/NCHS reference crosswalks between ICD-9-CM and ICD-10-CM; they help translate data and compare old and new codes, but they are not a substitute for coding from the medical record.
Key takeaways
- Fiscal year N runs from October 1 of year N-1 to September 30 of year N, so FY2027 codes take effect on October 1, 2026.
- Each update can add, revise and delete codes; a deleted code is no longer valid for dates of service in the new fiscal year.
- The code set in effect on the date of service (the discharge date for inpatient stays) decides which codes are valid.
- GEMs are a reference for translating and comparing data, not a coding tool; many mappings are approximate or one-to-many.
ICD-10-CM is a living code set. Medicine changes, and so do the codes. Two topics come up whenever codes change: the annual fiscal-year update, and the GEMs crosswalks that connect ICD-10-CM to its predecessor, ICD-9-CM.
The fiscal-year update cycle
The ICD-10-CM update follows the US federal fiscal year:
- Fiscal year N runs from October 1 of year N-1 to September 30 of year N. For example, FY2027 runs from October 1, 2026 to September 30, 2027.
- The annual update takes effect on October 1. CMS can also implement a mid-year update effective April 1.
- Each update can add new codes, revise code titles, delete codes, and change instructional notes, the Alphabetic Index and the Official Guidelines.
The files for each release (the code tables, the Tabular List, the Index and the addenda listing the changes) are published by CMS and NCHS ahead of the effective date.
How changes are proposed
Proposals for new and revised ICD-10-CM codes are presented at the ICD-10 Coordination and Maintenance Committee meetings, which are public. NCHS leads the diagnosis (ICD-10-CM) part and CMS the procedure (ICD-10-PCS) part. After the meeting there is a public comment period before final decisions are included in a release.
What a change means for coding
- A deleted code is not valid for dates of service in the new fiscal year. It is usually replaced by one or more new, more specific codes.
- A revised code keeps its code value but its title or notes change, which can change what it covers.
- A new code may expand a category, so a code that was complete last year can become a header that now needs more characters.
The code set in effect on the date of service determines validity. For inpatient stays, use the code set in effect on the date of discharge.
ICD Code Finder shows the current fiscal year on every page, marks codes that are new or revised this year, and lists all added, revised and deleted codes on the FY updates page. Pro users can get email alerts when an update changes codes in their saved code sets.
What GEMs are
The General Equivalence Mappings (GEMs) are reference files created by CMS and NCHS for the transition from ICD-9-CM to ICD-10-CM, which took effect on October 1, 2015. They come in two directions:
- Forward mappings, from ICD-9-CM to ICD-10-CM.
- Backward mappings, from ICD-10-CM to ICD-9-CM.
Each mapping row carries flags that describe the relationship, such as whether the match is approximate, whether there is no map, and whether a combination of codes is needed to express the same meaning.
What GEMs are for, and what they are not
GEMs are useful for:
- Translating historical data, research datasets and reports between the two code sets.
- Comparing trends across the transition.
- Converting lists that were built on ICD-9-CM, as a starting point for review.
GEMs are not a coding tool. Because many mappings are approximate, or map one code to several, a crosswalk result cannot replace coding from the medical record. Every code still has to be found in the Alphabetic Index, verified in the Tabular List and checked against the Official Guidelines.
ICD Code Finder provides a GEMs crosswalk in both directions, with the mapping flags shown, so you can see when a mapping is approximate or part of a combination.
Frequently asked questions
When do new ICD-10-CM codes take effect?
The annual update takes effect on October 1, the start of the federal fiscal year. CMS can also implement a mid-year update effective April 1 when needed.
Which code set applies to a claim that spans October 1?
For inpatient stays, the code set in effect on the date of discharge applies. For outpatient services, use the code set in effect on the date of service.
Can I code a patient record using GEMs?
No. GEMs translate between code sets for data and research purposes. Many mappings are approximate or map one code to several, so each case must still be coded from the documentation using the Alphabetic Index, the Tabular List and the Official Guidelines.
Where can I see what changed this fiscal year?
The ICD-10-CM release files from CMS and NCHS include the tables of new, revised and deleted codes. ICD Code Finder lists them on its FY updates page, and code pages carry New and Revised badges.
Informational, not coding advice. This page summarizes ICD-10-CM conventions for education. Always code from the medical record using the current ICD-10-CM Tabular List, Alphabetic Index and Official Guidelines for Coding and Reporting, plus payer policy.
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