Note: Payment terms that are configured on AR terms cannot be deleted. If you need to delete a payment term that is in use load the 'References' tab to see where the term is in use and change the AR terms using it to instead use an alternate payment term. Once a payment term is no longer in use by an AR term it can be deleted.
Under the Payment Terms heading on the left select the payment term you wish to delete
Under the Payment Terms heading on the left click the icon
On the confirmation dialog that appears select Yes