On the invoicing screen, use the "Jump to Invoice" function to locate a specific invoice, or use the "Show Invoices" drop down to filter invoices held in MIDAS and locate your invoice from the results.
Finally, click/tap the invoice's corresponding icon. After being prompted for confirmation, the selected invoice will be deleted.
Warning: Once an invoice has been deleted, it is removed from the system, and can only be retrieved by restoring the database to an earlier point in time. See Manage Database Settings