September 19, 2019
Add-on codes are a CPT or a HCPCS procedure code which describes an additional service associated with a primary or parent procedure code. The primary/parent procedure code represents the main service being rendered and the add-on code represents an additional service, whether represented by a time factor (additional minutes) or an additional surgical procedure such as the following:
- Each additional lesion removal
- Each additional graft
- Each additional vertebral section
- Each additional vein or artery
- Each additional pathology slide
The primary/parent procedure code denotes the majority of a service provided on a specific date of service and the add-on code, with a few exceptions, is also billed on the same date of service as the primary/parent procedure code.
Add-on codes can be identified several ways:
AMA CPT Professional Codebook:
- Identified by the plus symbol (+) notation next to the code
- Appendix D lists a summary of add-on codes
- Primary/parent codes associated with these add-on codes are found in a parenthetical note after the add-on code listing which codes are appropriate to bill as the primary/parent code to the add-on code
CMS Add-On Code Listing:
- A list of add-on CPT and HCPCS codes identified by CMS are found on a link at the bottom
- Add-on codes are identified in the CMS National Physician Fee Schedule with a Global Days indicator code of ZZZ
Common phrases used to identify add-on codes:
Both CPT and HCPCS procedure codes that are add-on codes can also be identified by key phrases in the code description, such as but not limited to:
- List separately in addition to primary procedure
- Each additional
- Done at time of other major procedure
When billing add-on codes for reimbursement include:
- Add-on codes must be billed with an appropriate Primary/Parent code on the same claim on the same date of service as the primary/parent code. The add-on code will be denied reimbursement if not billed with the correct primary/parent code. There are some exceptions to this which can be found in the CPT codebook
- Add-on codes are exempt from multiple procedure reduction and therefore modifier 51 is not appropriate to append to the add-on code
- No modifiers appended to an add-on code bypass a denial of an add-on code
When billing add-on and primary/parent code combinations, if the primary/parent code is denied reimbursement the add-on codes will also be denied.
Review the Add-On Codes” Payment policy and the CMS listing of add-on codes.