The purpose of this article is to provide the steps to VOID a closed transaction as there is no option to delete.
Navigate to Sales>>Processing>>Sale Transactions
Find the sale in the Closed view or in the ALL view if the sale closed more than 60 days ago.
Once highlighted, select the Void button.
If the sale closed in a previous month, and you want the sale to be voided in the previous month as well, then change your Processing Date, back to the Payment Received date in the original sale prior to clicking the Void button.