Credit Notes Against Already Invoiced Order or Line of Stock Process

Scenario: We receive stock from a supplier processed and invoiced through POP, we start selling the product and find out there&s an embellishment and the supplier then provides a discount for one of the products. We no longer have the full amount of goods to &return& so we can credit out the order and re-debit therefore, the only option would be to make a stock adjustment for items sold and then, after processing the return and new order, write the stock off. We&d also have to create a new nominal for Stock Issues. This is just incredibly messy and feel there should be a better way to deal with a simple credit notes against stock items.