You can cancel a Purchase Order in the system. To go through with this, you need to check that the PO in question meets specific requirements. In this regard, you need to pay attention to the PO status. It has to mark "Open."
On the other hand, if it is already received or partially received, you will need first to unreceive it, and only then will the status change to open.
To unreceive a PO, you will be required to look into the parts within the PO and corroborate that they are not already booked to a WO. you will need to go into the WO and unlink it. After having unreceived the PO, the "Cancel" option will appear.
