Purchasing & Inventory: Cancelling/Reverting purchase orders

Hi Community,   I got a question from the lovely @Anthony Gerald Fernandes​:   "hi rozz, Just need to know if we can cancel or revert back the purchase order once posted? by mistake it was posted, but we didn't receive the order. would be of much help for me.​ thanks."    Please may someone help him? 😊   Best, Rozz