When you receive inventory into a purchase order, it will automatically change the status from open to either partially received or closed. If you need to change it to another status or want to create a custom status follow these steps:
In the purchase order, click on Edit.
Then select Switch to Advanced Mode.
In the Status field, type the desired status. You can also enter a custom status.
Then save your purchase order at the bottom of the form.
When your purchase order saves, you see your updated status.