If you have a one time charge you want to change for an item when a customer places and order independent of the quantity of an item they order then you could use the price charges on the price discount journals. This could be used for example as a order fee for an item you don’t normally stock, some sort of handling fee, or you could use it to if the customer doesn’t order a minimum quantity. This is a quick walk through of the effect of the price charges field when setting up a trade agreement.
Cheers
Lachlan