Billing Fundamentals/Foundation/20 minutes/Reviewed 2026-07-10

ICD-10, CPT, and HCPCS: What Each Code System Does

Understand diagnosis, inpatient procedure, professional service, supply, drug, and equipment code-set roles without mixing them.

Quick answer

ICD-10-CM reports diagnoses, ICD-10-PCS reports inpatient hospital procedures, CPT reports many physician and outpatient services, and HCPCS Level II reports supplies, drugs, equipment, and other services not represented in CPT.

Rules to know

Use the code set effective for the date of service or discharge.
Code-set inclusion does not establish coverage.
CPT is maintained and copyrighted by the AMA; use a licensed current codebook.
HCPCS Level II files and ICD-10 files are published by federal sources.

Operational workflow

01Identify claim type and setting.
02Select diagnoses from current ICD-10-CM guidance.
03Select the applicable procedure or supply code set.
04Apply official conventions, instructions, and payer policy.
05Validate effective dates and documentation support.

Common failure modes

Assuming a valid code is automatically covered.
Using an outdated annual code set.
Choosing a diagnosis only because it appears on a payer edit list.

Knowledge check

Which code set reports diagnoses across covered entities?

ICD-10-CMHCPCS Level IIPlace of ServiceCARC

Official sources

ICD-10 Code Files and Official GuidelinesCenters for Medicare & Medicaid ServicesReviewed 2026-07-10 HCPCS Release and Code SetsCenters for Medicare & Medicaid ServicesReviewed 2026-07-10 Adopted Standards and Operating RulesU.S. Department of Health and Human ServicesReviewed 2026-07-10

Continue this track

FoundationThe Medical Billing Claim Lifecycle IntermediateClean Claim Scrubbing Checklist FoundationHIPAA Privacy and Minimum-Necessary Billing Workflows

Education only. Verify the current code set, payer contract, coverage policy, implementation guide, and claim-specific facts. Do not enter protected health information into this site.