All of the following are correct regarding add-on codes except:

• A. They can be reported as stand-alone codes
• B. They are used to add information to the main code
• C. They must be appended to a primary code
• D. They can be used for performance measurement

Answer: (A)

Add-on codes are used to capture additional procedures or service components that accompany a primary procedure, providing extra detail about work performed beyond the main service. Because they relate to the primary code, they must always be attached to a primary code and cannot be reported by themselves. That means they add information to the main code and must be appended to it. They are not stand-alone codes, which is why the statement about stand-alone reporting is not correct. The requirement to attach them to a primary code is exactly how add-on codes are used in billing. They can also be used for performance measurement because including the add-on work with the primary procedure helps reflect the full scope and resource use of the encounter in reporting and quality measures.