What is the primary function of a modifier in CPT coding?

The primary function of a modifier in CPT coding is to provide additional information to the third-party payer. Modifiers enhance the basic description of a procedure or service by adding important details that may affect reimbursement or the payment process. For example, a modifier can indicate that a procedure was performed on a specific part of the body or that the procedure required additional effort or complexity.

Using modifiers helps ensure that the payer understands the circumstances surrounding the service provided, which can lead to appropriate payment decisions. This specificity is critical for accurate billing and coding, as it clarifies any variations from the standard procedure definitions.

Other options do not capture the essence of what a modifier does. While a modifier does not change the fundamental CPT code itself (which is reflected in the first choice), it does provide important nuances rather than altering the code. It also does not categorize procedures, as that's typically done by the structure of the CPT code itself. Finally, while modifiers may clarify situations that could be seen as billing errors, their main function is to communicate precise details regarding the service rendered, rather than indicating mistakes in billing.