Credit Memos / Vendor Credits / Void

Not sure if this is the right place, but I'd to be able to create and apply credit memos to my AR invoices and vendor credits to my AP invoices. It would also be nice to be able to void them. Right now the only options appear to be either retroactively altering or deleting historical invoices (a no-no for accountants), or some roundabout way where I have to create a clearing account in my banking or credit card sections and then following up with a journal entry to zero it out. 

It would be nice to have the option directly in the AR/AP modules to apply credit memos/vendor credits on open invoices.