This list of CPT® modifiers and definitions includes two-character medical modifiers. The American Medical Association (AMA) maintains the Current Procedural Terminology (CPT®) code set.
CPT® code modifiers allow you to indicate a service or procedure did not occur exactly as described by a HCPCS or CPT® code descriptor. In other words, use these procedure code modifiers appended to a code to show a specific circumstance altered the service or procedure, but the circumstance did not change the code that applies. Modifiers may affect payment or they may be informational only. You may use more than one modifier on a single code when documentation supports doing so.
CPT® code modifiers typically are two digits, in contrast to HCPCS modifiers, which are alphanumeric. There are exceptions, with CPT® Category II modifiers and anesthesia physical status modifiers being alphanumeric.
Payers may have different rules about modifier requirements based either on the modifier itself or on the specific service or procedure performed.