I need to get some info on the GY modifier. First of all I bill for an acupuncture office and I'm not sure if I'm doing it correctly. I know this modifer is used for Medicare. Can someone give me some clarification? I billed the regular acupuncture codes and didn't know the patient's insurance info was their supplemental insurance. The claim was denied and needed the EOB from Medicare in order to pay the claim. I didn't include the GY in the claim to begin with. How do I know when to use the GY? Do I need to verify with the insurance that the patient coverage is their supplemental to Medicare??