On the invoice, click Delete in the Patient Rebates section and confirm the deletion.
NOTE: You can only delete patient rebates if it is done on the same day. After that, you need to call Medicare on 1800 700 199. For a bulk bill or DVA rebate, Medicare does not allow this to be done manually. You need to call them on 133 254 for DVA and 1800 700 199 for Medicare, and then they can cancel it at their end.