A Purchase Order which is either created, approved or ordered can now be canceled in ServiceDesk Plus OnDemand.
To cancel a purchase order,
Go to Purchase. This opens the purchase order list view page.
Open a purchase order which you would like to cancel, click Actions >> Cancel.

You can choose whether you want to notify the approvers upon canceling a purchase order. Also, the technician needs to provide with comments on why the purchase order is canceled. The comment section is a mandatory field. The PO owner will be notified by default if the purchase order is Approved/Rejected/Canceled.
The status of the purchase order will automatically change to Canceled.