Sometimes ebay will send it automatically, but sometimes not. Other times (it happened to me recently) where 3 invoices were sent to me but I didn't get any of them. I had gotten an open case put on me, checked everything and found no invoice and it was a multiple item win. I sent a message to the seller to send an invoice and he said he sent 3 already. Not sure if some went to the spam folder or what.
I am glad tho ebay made open cases close automatically once payment was sent, but also annoyed that ebay automatically opens cases 24 hours after the auction ends.