Yes, you can receive partial quantities as well as close a Purchase Order without having received everything.
- Navigate to Restock > Purchase Orders
- Click into the details of your Submitted purchase order
- Navigate to the Receipt of Goods tab
- Under 'How Many Received' fill in what has been received
- Please note that once the PO has been closed, it cannot be opened back up. So if you have input the total amount received and you are not expecting to receive more, click the 'Mark PO Closed' button.