Guides CM vs PCS
ICD-10-CM vs ICD-10-PCS
They share a name and an October 1 release date, and almost nothing else. ICD-10-CM classifies diagnoses and is maintained by CDC/NCHS with CMS; ICD-10-PCS builds inpatient procedure codes from seven character positions and is maintained by CMS alone.
The short answer
ICD-10-CM codes the condition. ICD-10-PCS codes the procedure. A patient admitted with acute appendicitis has that diagnosis coded in ICD-10-CM; the appendectomy performed during the admission is coded in ICD-10-PCS. They are two separate code sets that happen to share the “ICD-10” prefix and an annual October 1 effective date.
Only ICD-10-CM descends from the World Health Organization's ICD-10. ICD-10-PCS has no WHO counterpart at all — it is a United States procedure system developed for and published by CMS, and its structure looks nothing like a WHO classification.
Side by side
| ICD-10-CM | ICD-10-PCS | |
|---|---|---|
| Codes | Diagnoses and reasons for encounter | Inpatient hospital procedures |
| Maintained by | CDC / NCHS, with CMS | CMS |
| Length | 3 to 7 characters | Exactly 7 characters |
| Punctuation | Decimal point printed after the third character | None — written as one unbroken string |
| First character | Always a letter | A digit or a letter, depending on the section |
| Structure | A hierarchy: chapter, block, category, code | Seven independent axes, constrained by published tables |
| Partial codes | Categories exist but are usually not valid for submission | No partial codes — a code is seven characters or it is nothing |
| Update cycle | Annual, effective October 1 | Annual, effective October 1 |
| Current release here | FY 2027 — 98,403 entries | FY 2027 — 80,174 entries |
| Example | E11.9 — Type 2 diabetes mellitus without complications | 0DTJ0ZZ — Resection of Appendix, Open Approach |
| Browse | ICD-10-CM index | ICD-10-PCS index |
Telling them apart on sight
Written out, the two look quite different. An ICD-10-CM code opens with a letter and, if it runs past three characters, prints a decimal point:
A seven-character string that starts with a letter can fit both patterns. Stripped of its decimal point, an ICD-10-CM code such as E08.37X1 is seven characters of letters and digits — exactly the shape of an ICD-10-PCS code. That is why search here checks a code-shaped query against every set it could belong to rather than guessing, and why the code set is always named on the result. More on that in How to Search ICD-10 Codes.
How they work together
On an inpatient hospital claim the two sets are used side by side, describing different facts about the same stay. ICD-10-CM carries the diagnoses: the condition that occasioned the admission, plus any additional conditions that affected the stay. ICD-10-PCS carries the procedures performed during it. Neither substitutes for the other, and neither is derived from the other — a diagnosis does not imply a procedure code, and a procedure code does not encode why the procedure was done.
Outside the inpatient hospital setting, procedures are reported with CPT and HCPCS Level II instead of ICD-10-PCS, while ICD-10-CM continues to carry the diagnoses. So the diagnosis set is near-universal, and the procedure set depends on where the care happened.
Four common confusions
- “ICD-10” on its own is ambiguous in the U.S. It might mean the WHO classification, ICD-10-CM, or ICD-10-PCS. In an American billing context it usually means ICD-10-CM — but not always, and on an inpatient claim both are in play.
- ICD-10-PCS is not “the procedure half of ICD-10-CM”. They are separate publications, from partly different maintainers, with different files and different rules.
- The billable/specific label is an ICD-10-CM idea. ICD-10-PCS has no equivalent because there is no such thing as a partially specified PCS code. See What Does a Billable/Specific ICD-10 Code Mean?
- Sharing an effective date does not mean sharing a change list. Both take effect October 1, but each has its own additions, revisions and deletions. Compare FY 2027 for ICD-10-CM with FY 2027 for ICD-10-PCS.
Official sources
Where the facts on this page come from. MedCodeSearch is an independent reference service; these organizations publish the code sets themselves.
- CDC — National Center for Health Statistics
NCHS is responsible for the U.S. clinical modification of the ICD diagnosis classification.
- CMS — ICD-10 codes
CMS publishes the ICD-10-PCS files and the annual ICD-10 update materials.
Look up a code
Search every current ICD-10-CM, ICD-10-PCS and HCPCS Level II code, or browse a set from the top of its hierarchy.
Browse ICD-10-CM Browse ICD-10-PCS Browse HCPCS Level II Code updates
This guide explains how the code sets are built and published. It is not coding, billing, legal or medical advice, and it never recommends a code for a specific patient or claim. See the Disclaimer and Methodology pages.