When you Unconfirm an SO, any stock that may have been marked as Reserved will be moved to Available. This also prevents lines being packed, shipping labels being printed and invoice generation. Therefore, unconfirming and cancelling and deleting an SO is only available for unpacked and uninvoiced SO’s.
Likewise, when you Cancel an SO, any stock that may have been marked as Reserved will be moved to Available.
The main difference between Cancel and Unconfirm is intention. If you want to continue working on the SO but don’t want any action to be taken, then Unconfirm will do this. If the idea is the stop working on this SO completely then Cancel is more appropriate.
(Note, Cancel can be reversed by Uncancelling, unlike Deleting which cannot be reversed)
There are two ways to go about Cancelling or Unconfirming an SO:
Go to the SO page, click the settings icon (white gear, on red background), and from there you can Unconfirm or Cancel the SO. If you cancel you will be presented with a checkbox to delete the SO.
From the Sales Order table, select multiple SO’s using the checkboxes on the left. Then on the action bar, you can click Unconfirm (or Confirm, as appropriate) and under the Close menu, click Cancel to cancel the selected SO’s. If you Cancel you will be presented with a checkbox to Delete.