Not sure if there a reason, but why can we not have a credit note Module where you can post credits instead of only from a related invoice?
I can see the benefit of it as well, but sometimes you wont have a clue from which invoice goods was returned from, or in our case we send products on pallets to customers and invoice them for it and when they return we will not know from which exact invoice it was returned from. We did a combined credit for all pallets returned on one credit note on previous accounting software.
With all integrated ERPNext i think it should still be possible to check that not more are credited as being invoiced, but to have separate to monitor a credit sequence will be much easier than mixing with invoices on system.
Hope someone could help.