How to CN a batch of return items from different invoice

[ronwong]

I am sorry, this is more of a business question, but I have a customer who orders various items on outright sale, then they want to return unsellable items at the end of the year from things they bought along the way, is there a way to CN them? The easy way would be to give them an outright amount CN which does not match any stock, and just write off what they return. But this way, this customer will be a loss making customer and we cannot keep track how much we make from them.