To view the details of an order, double-click on it in the order summary (or highlight it and press 'View Order').
The 'Totals' tab allows you to see at a glance the effect of any changes to order lines, shipping or tax on the total value of the order.
The 'Original' column lists the details as they appeared when you first downloaded the order. The 'Current' column shows the effect of any changes you have made.
It is here that you can allocate a percentage discount. The discount will always be calculated on the value of the order lines (excluding any shipping/tax) Actinic will automatically calculate new amounts for all other charges, where appropriate.
Drop-down lists allow you to change the shipping and handling tax status if necessary.
Note: There may be a slight discrepancy between the tax value shown here and the one shown in the order line details in 'Line Items' tab. This is just due to the tax rounding rule selected (in Business Settings | Tax) and is not critical. For tax purposes (in the UK) tax is calculated after any discount has been deducted.