Navigation: Bookkeeping > Select Client > VAT/MTD VAT > Submit VAT
Head to either VAT or MTD VAT section from the navigation above then select 'Submit VAT' from the drop-down menu.
Once there, use the Action drop-down menu and you will find the 'Delete' option under a particular VAT period. It's also worth noting that you can only delete the most recent period. So if you want to delete a period which pre-dates the most recent, you will need to delete the most recent first.