Why:
Suppliers can be deleted if they cease trading or become unreliable.
Where:
Deletion can be performed from the Supplier List Window. To access the list simply click the Supplier View button.
How to Delete a Supplier:
Note! When a supplier is
deleted the system does not check whether there are open orders against that
Supplier. You must make sure none exist before deletion.
From the Supplier View, highlight the supplier that you
would like to delete & select Supplier > Delete from the menu or
right-click on the supplier and select the Delete command. Alternatively,
select the supplier and click the Delete button 
. A confirmation window will now appear, there
you should select ‘Yes’ to finish deletion.