You can cancel a sales order if the customer no longer wishes to purchase the items from you. See the video to show you how to do this. There are also step by step instructions below the video.
Steps
Ensure the payment for the order is deleted or, in the case of an authorised credit card payment, refunded.
Click the red delete button at the top of the sales order to delete it.
If the sales order is linked to a purchase order, confirm in the popup that you still wish to delete the sales order.