CMS Pub. 100-04, ch. 4, § 20.6

Modifiers are two-digit identifiers that are reported with CPT and HCPCS Level II codes

to provide additional information about how an item, procedure, or service is provided,

and improve the accuracy of coding. These two-digit modifiers can be alphabetic,

numeric, or a combination of both. The use of modifiers is not limited to certain code

sets. Specifically, CPT modifiers may be used with HCPCS Level II codes when

appropriate. Similarly, HCPCS Level II modifiers may be used with CPT codes to

appropriately describe how an item, procedure, or service is provided. Providers may use

any applicable modifier where appropriate. For Medicare purposes, modifiers are used

either as pricing or informational/tracking indicators.

The Integrated Outpatient Code Editor (I/OCE) accepts all valid CPT and HCPCS Level

II modifiers on OPPS claims. As of April 1, 2023, there are approximately 410 active and

valid modifiers. Definitions for all valid modifiers may be found in the latest CPT and

HCPCS Level II code references. The complete descriptions for all CPT modifiers can be

found in the latest CPT code book. Alternatively, the complete descriptions for the

HCPCS Level II modifiers can be found in the latest HCPCS Level II code book, as well

as in the latest HCPCS Level II code file that is available on the CMS HCPCS website,

specifically, at https://www.cms.gov/medicare/coding/hcpcsreleasecodesets/hcpcs-quarterly-update. Additional guidance on the use of modifiers can also be found on the

Medicare Administrative Contractors’ (MAC) websites. Note that, under the OPPS, the

use of modifiers applies to services/procedures performed on the same calendar day.

The following subsections provide information on the use of certain modifiers under the

hospital OPPS. For information on additional modifiers not described below, refer to

your MAC website(s) for guidance.