ICD-10-CM vs ICD-10-PCS
ICD-10-CM is the diagnosis code set used in every healthcare setting. ICD-10-PCS is the procedure code set used only for inpatient hospital procedures.
Last reviewed May 24, 2026
Side by side
ICD-10-CM
Clinical Modification — the diagnosis code set used in every U.S. healthcare setting. Maintained by CDC's National Center for Health Statistics.
ICD-10-CM- Used on every encounter type (inpatient, outpatient, ED, office).
- Three to seven characters, alphanumeric.
- Annual update each October.
ICD-10-PCS
Procedure Coding System — the procedure code set used only for inpatient hospital procedures. Maintained by CMS.
ICD-10-PCS- Used on the UB-04 inpatient claim only.
- Seven characters, alphanumeric, multi-axial structure.
- Not used in physician office, ASC, or outpatient settings (those use CPT/HCPCS).
When to use ICD-10-CM
- Any encounter requires a diagnosis code — ICD-10-CM is universal.
When to use ICD-10-PCS
- Coding an inpatient hospital procedure for the UB-04 — ICD-10-PCS is required.
Common mistakes
- Trying to use ICD-10-PCS in an outpatient setting (use CPT instead).
- Confusing the two code sets in vendor documentation — the file extension and update cadence differ.
- Forgetting that the annual update is October 1 (not January 1 like CPT).
Sources
- CDC — ICD-10-CM Browser Toolhttps://www.cdc.gov/nchs/icd/icd-10-cm/
- CMS — ICD-10-PCShttps://www.cms.gov/medicare/coding-billing/icd-10-codes
Related
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This comparison is a research aid for billing and compliance staff. It does not provide legal, medical, or financial advice and does not replace counsel. References cited link to primary sources at CMS, HHS, OCR, eCFR, NIST, and the relevant payer or state regulator. Last reviewed May 24, 2026.