Add-on codes are procedure codes that are always performed in conjunction with a primary procedure. Significantly, add-on codes are NOT subject to the multiple procedure reduction rule (i.e. full reimbursement).

Add-on codes cannot be considered the primary procedure when determining proper reimbursement as by definition add-on codes must be “listed separately in addition to the primary procedure.”

In the CPT Manual, add-on codes are designated by the “+” symbol and generally include code descriptors including phrases such as “each additional” or “list separately in addition to primary procedure.”

In the New York Worker’s Compensation Medical Fee Schedule, add-on codes are designated by the “+” symbol.

In the New Jersey Fee Schedule, add-on codes are designated by the “X” symbol. However, it should be noted that some codes have been designated as add-on codes post-creation of the New Jersey Fee Schedule. Therefore, the New Jersey Fee Schedule guidelines direct you to the CMS website to check for updates. The most updated list of add-on codes can be found here.