Modifier Billing Guide: Appropriately Bill Your Modifiers:

Modifiers used in medical billing and coding are the alpha or numeric character that coincides with the appropriate CPT code. 

If you do not use these modifiers appropriately, coding and billing errors will occur. Issues with fraud and compliance may also arise when you are billing and coding.

To be sure you are billing modifiers at the appropriate time, the below link will direct you to a Modifier billing guideline.

This guideline lists the modifiers by specialty and the appropriate time to bill the modifier with the specialty: Modifier Billing Guide