If, for any reason, the project is canceled or you no longer need to order products, you can delete a purchase order (PO) in the Draft or Draft Completed status. Deleting is permanent; you cannot retrieve the deleted PO.
When you delete a PO, Cloud moves the products in the PO to the "Ready to Order" status, and they appear on the "Procurement > Ready to Order" tab in the left navigation menu.
To delete a PO, go to "Procurement > Purchase Orders" in the left navigation menu. Click the 3-dot menu in the PO tile or row and click "Delete."
To download a copy of the PO before deleting it, see this article.
If you use Inventory Management and want to delete a PO that is either "Partially Received" or "Received" with items already checked in, Cloud prompts you to choose the inventory location (pool-tracked item) or the item (asset-tracked item) and provide a reason for decreasing the quantity.
Check out this article for more details.