Multiple Modifiers – CPT Modifier 99

This modifier is used when the modifier field on the claim form has been exhausted. If you need that much room to add modifiers, add the 99 modifiers to the last accessible area and include a characterization of the other modifiers required on the claim.
Multiple Modifiers – CPT Modifier 99
In some scenarios, two or more modifiers may be required to define a service entirely. In such case scenarios, CPT modifier 99 must be added to the basic procedure, and any other applicable modifiers should be listed as part of the program description.
Modifier -99 may apply to a specific service. The impact of payment or jurisdiction may be determined by the additional modifier(s).

medical billing, modifier 99