How are unlisted procedure codes designated in the CPT coding system?

In the CPT (Current Procedural Terminology) coding system, unlisted procedure codes are designated by the use of specific codes that end in "99." This numbering convention indicates that the code does not correspond to a specific procedure that is otherwise listed in the CPT. Unlisted codes are created to account for procedures or services that are not well-defined or recognized by a dedicated code, allowing for flexibility in coding for unique or new treatments.

Utilizing a code that ends in "99" serves to signal to payers that the procedure is atypical or does not fit into the established categories within the CPT. This is significant for documentation and billing purposes, as it prompts further description and clarification of the procedure being billed.

Other options do not accurately reflect how unlisted procedure codes are categorized in the CPT system, thus reinforcing the importance of recognizing "99" as the definitive ending for these unlisted codes.