You can discount individual services or retail products by price or percentage by applying the discount by line item
Just select either the £ or % and then type in the amount you want to discount by. The discount is automatically deducted from the line item and total bill.
The £ is highlighted when you've selected an absolute amount discount (£10 below):
The % is highlighted when you've selected a percentage discount (10% below):
To discount the total bill by a % amount, simply add in the discount for every line in the bill: