Can seller create new invoice for buyers "files" AFTER items paid for and shipped...?

[goldenegg178]

I have a buyer who simultaneously won three different lots from me in one day. It was made very clear to them that I was going to send them a revised invoice that would have combined shipping, to save them money on shipping. I stressed to them do NOT pay until I send revised invoice with combined shipping. ***BUT  they soon went ahead and paid each item individually, therefore of course FAR overpaying on total shipping, as I was going to combine shipping for them and save them alot of money..... 

I found that by them not waiting for my revised invoice - they had overpaid $12 in shipping. So I have done a Pay Pal refund of $12 for their shipping overpayment. They seem happy. And items are shipped and on their way. Sounds like all is well....BUT now the buyer has asked if I can send them a "final invoice" that shows the revised shipping etc, for their files..... I have gone on Ebay and cannot  find how to make a revised invoice AFTER auctions have successfully been completed, paid for and shipped to the person....I know that I have "revised" invoices easily in past - but think that was always before someone paid.....Is there a way to create through Ebay a revised invoice, for such auctions that are already paid for and shipped off???    If not - I figure that I can always type up one the old fashioned way on the computer and mail it to them....but seeking if there is a way to still do a revised invoice (post auction payment and shipping) through the Ebay system? Thanks !