I've added modifiers plenty of times without asking the provider first. My understanding is the modifier conveys something to the insurance company, it is not a medical decision or something of that nature. For example, when a PT renders manual therapy in addition to other services, I add a 59 modifier, when an MD see a patient for a routine physical and on the same day for a sick office visit, I add the 25 modifier, however in certain cases I wouldn't take the iniative like adding a 22 modifier because the notes indicate the patient was obese. If you're unsure as to whether it's appropriate, ask a supervisor or the provider however I wouldn't think most modifiers especially one indicating you're billing for a global service would require a doctor to add it.