You can BILL Medicare whatever you want, it's what you do after Medicare makes payment that is crucial.
If you are a participating provider, you cannot bill the patient any higher than the allowed amount.
If you are a non participating provider, you cannot bill the patient any higher than the limiting fee, which is 115%.
You can BILL Medicare your regular fees, the same as you bill the other commercial carriers, but you must write off anything over the allowed amount once the claim is processed.
Hope that clears it up.
Michele