How it works
CPT Category I codes are five-digit numeric codes for established services. Category II codes are optional tracking codes for performance measurement, and Category III codes are temporary codes for emerging technology. The code set is updated every year, with most changes taking effect on January 1. In Medicare’s HCPCS system, CPT forms Level I.
Why it matters
CPT codes, together with modifiers, define what was done and drive most professional payment. Using deleted codes, or missing new ones, causes denials at the start of each year.
Example
A new code is created for a procedure that was previously reported with an unlisted code. From the effective date, claims must use the new code, and the fee schedule needs an entry for it.