What Is HCPCS? Level I and Level II Codes Explained for Coders

The federal HIPAA code set rule spells HCPCS out as the Health Care Financing Administration Common Procedure Coding System.

The rule at 45 CFR 162.1002 defines the standard for physician services as "the combination of Health Care Financing Administration Common Procedure Coding System (HCPCS), as maintained and distributed by HHS, and Current Procedural Terminology, Fourth Edition (CPT-4)".

CPT-4 itself is maintained and distributed by the American Medical Association.

The regulatory name matters mainly because it shows what the set is and who the federal rule puts behind it.

For the work itself, the structure is what counts: CMS describes HCPCS as divided into two main subsystems, Level I and Level II.

The set is not a claim form and not a payer — it is the vocabulary those forms carry.

On a claim, the two levels divide the vocabulary.

CPT describes the services and procedures performed by physicians and other qualified health care professionals, and Level II names what the encounter involved beyond that work — the transport, the equipment, the supply, the drug product.

The two levels split the code set's work.

Level I is CPT, maintained by the AMA; Level II is a standardized system for products, supplies and services not in CPT, with ambulance services and DMEPOS as CMS's examples.

HHS designated CPT under HIPAA as a national code set for physician and other health care professional services and procedures.

The formats differ at a glance.

All CPT codes are five characters, numeric or alphanumeric depending on the category, while a Level II code is a single alphabetical letter followed by four numeric digits.

Side by side:

Under the HIPAA rule the two levels work as one standard: physician services are reported with the HCPCS and CPT-4 combination together, not one level or the other.

CMS maintains HCPCS Level II codes, including the decisions about additions, revisions and deletions — that is CMS's own statement of its role.

Level I answers to a different table.

CPT is maintained by the CPT Editorial Panel, an independent group of clinical expert volunteers appointed by the AMA Board of Trustees.

The split matters operationally.

The level a claim line uses tells you which body's process changed it — an AMA panel decision for CPT, a CMS quarterly file for Level II (with the CDT dental exception described below).

One slice of Level II sits outside CMS's pen: CDT dental codes are considered HCPCS Level II codes, but the ADA — not CMS — decides their additions, revisions and deletions.

For coding guidance rather than maintenance, hospital coders also work with Coding Clinic for HCPCS, published since 2001 by the American Hospital Association's Central Office and produced cooperatively by the AHA, AMA, AHIMA and CMS.

It covers CPT and certain Level II codes for hospital providers.

Level II exists for what CPT does not describe.

CMS calls it a standardized system for products, supplies and services not in CPT, and its own examples — ambulance services and DMEPOS — show the range: this is the level that names what gets transported, equipped, supplied and administered.

Drugs and biologicals have their own track inside the level.

CMS runs a standing application calendar for Level II drug and biological code applications — the door new products use to get codes of their own.

Two letter series show how CMS uses the set.

G codes identify professional services that would otherwise be coded in CPT but have no CPT code, and CMS establishes them internally rather than by application.

C codes are the facility counterpart.

Hospitals report drugs, biologicals, devices and new-technology procedures with them under the hospital outpatient PPS (OPPS), and non-OPPS hospitals and CAHs may report them at their discretion.

Level II knows its lane: under HIPAA's adopted code sets, diagnoses belong to ICD-10-CM and hospital inpatient procedures to ICD-10-PCS.

A CMS Medicare Learning Network summary draws the same map.

It puts HCPCS on procedures and services in the office, hospital outpatient, ASC and other outpatient facilities, while ICD-10-CM reports diagnoses on all claims.

One boundary matters early for coders choosing a path: inpatient facility work steps outside this system.

ICD-10-PCS carries the procedure coding on inpatient facility Medicare Part A claims, with HCPCS and CPT covering procedures in the other settings.

A biller or coder reaches for Level II whenever a claim line reports something CPT does not describe: ambulance services, DMEPOS, supplies, drugs and biologicals, or a professional service whose home is a G code.

The setting shapes how much of the day runs through Level II.

Hospital outpatient work adds the C-code layer under OPPS; ambulance and DME suppliers live in Level II by definition; an office practice meets it on drug, supply and G-code lines.

Even a routine office visit can carry one.

G2211, Medicare's add-on for inherent visit complexity, is reportable with office and outpatient E/M visits and, starting January 1, 2026, home or residence visits.

Level II modifiers are part of the same toolkit — CMS establishes them internally as alpha-numeric or two-letter codes, published with the code set file — and a biller appends one when the line needs more context than the code alone carries.

And this is not a Medicare-only vocabulary.

G codes are part of the national HCPCS Level II code set, and CMS notes non-Medicare insurers may use them too; the HIPAA rule embeds the code set in the national standard for physician services.

The training side runs through it as well.

AAPC says the CPC covers ICD-10-CM, CPT and HCPCS Level II across outpatient and physician services, and the only code books allowed on that exam are the AMA's CPT Professional Edition plus the candidate's choice of ICD-10-CM and HCPCS Level II books.

All of that makes HCPCS worth knowing beyond the code book: it is the vocabulary of the claim lines CPT does not describe.

You can see how employers phrase the skill in current medical coder jobs — and if you are mapping the wider role, the medical coder career guide covers settings, employers and the career path.

Level II moves on a quarterly rhythm: CMS publishes the official HCPCS Level II update as quarterly public-use files.

The October 2026 Alpha-Numeric HCPCS file was posted with a September 23, 2026 update date, following the January, April and July 2026 files.

Codes enter the set two ways: CMS's application process or internal creation.

The application calendar is fixed — drug and biological code applications are due the first business day of each quarter, in January, April, July and October, while non-drug and non-biological applications are due the first business day of January and July.

G codes and Level II modifiers skip the application line entirely, because CMS establishes both internally.

The quarterly release itself is leaner than it used to be.

CMS no longer publishes a Table of Drugs and HCPCS Index with the updates, because all Level II updates now ship as searchable, sortable electronic files.

Drug billing adds its own quarterly artifacts: CMS posts quarterly Medicare Part B drug payment limit files and NDC-HCPCS crosswalks, such as the October 2026 payment limit file and crosswalk.

The cadence is the compliance point: HIPAA requires covered entities to use the medical data code sets that are valid at the time the health care is furnished (45 CFR 162.1000).

A code that was valid in March can be revised or deleted by the July file.

That is why the quarterly drop lands on billing calendars alongside the CPT cycle, where most approved changes take effect each January 1 (some code categories follow other release schedules).

Career information for billing and coding professionals — not coding, billing-compliance, legal or tax advice. Confirm current HCPCS files, deadlines and code status with CMS, and payer-specific rules with the payer.