1. You can set Delivery Completed Indicator in Purchase Order or at time of
doing goods receipt. That simply means you cannot do further GR for that item.
You can still process Open Invoices .
2. You can block material at purchase order level which means, you will not
be able to do any GR , Invoice against that specific item in PO.
The recommended is the first option though.
Second option is used in case of : -
1. to cancel an item
2. An item is closed and can be archived