Add-on procedures are commonly carried out in addition to a primary procedure. The codes representing add-on procedures are identified in the American Medical Association (AMA) CPT book with a "+" symbol and are listed in Appendix D of the CPT manual. Add-on codes are always performed in addition to a primary procedure. They should never be reported as standalone codes. An add-on code billed without the accompanying code for the primary procedure may be contested. They are exempt from multiple procedure reduction rules and should not be billed with modifier 51.
Health Net does not require documentation at the time of claim submission; however, if the claim is audited, documentation may be required.
- AMA CPT Book