A coder is about to report a CPT add-on code for additional work described in the codebook. What reporting rule must be followed?

CPT add-on codes describe additional work associated with a primary procedure and must be reported with an appropriate primary code; they are not stand-alone services. They are typically exempt from modifier 51 multiple-procedure reductions per CPT conventions. Reporting an add-on alone, substituting it for the primary code, or routinely forcing modifier 51 contradicts standard CPT add-on guidelines. Coders should also honor any parenthetical primary-code restrictions listed with the add-on.