Apply a discount after ordering, with the refund handled for you

Customers can apply one of your store's discounts to an order they already placed. You choose which discounts to offer from a picker of your real active discounts, and customers only ever see discounts that are still live in Shopify. You also choose where the difference goes, the original payment method or store credit, and the customer is told which. The refund uses the amount Shopify shows as owed on the order. If a later change would quietly drop a discount the customer already has, that change is refused with a message naming the discount.