You are able to provide a surcharge to your cart once items have been added. These surcharges are able to be applied via a flat rate or a percentage.

The option to apply a surcharge is found within the "Add Modifiers" option which is below the Subtotal of the cart.

Simply click into there and you will find the option to apply a surcharge via flat rate or via percentage. You will also be able to provide the surcharge with a name and description.

The surcharge will then be applied to your cart and be calculated with the Subtotal of items before tax. These surcharges can be edited or removed upon being added if necessary.

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You will also find that you can apply a surchare to a line item's price, by either a dollar or percentage markup.