Hi Alibama,
It is not currently possible to send invoices directly from your Auctiva account. However, you can still send combined invoices through your eBay account, by going to the "Sold" section of your "My eBay" page, and selecting the "Send Invoice" option next to any of the items.
Any additional questions? Please file a support request using the appropriate link on our help page:
http://www.auctiva.com/free-auction-software-help/help.aspx-Mike