Hi,
On the order, fill in the amount to invoice and then under the Actions button, select Transfer. This will transfer any items with a quantity in the to Invoice field to an invoice, if that is the document you select.
Here's what I mean:
The next window is where you select which document type you're trying to create:
Click the Transfer button and an invoice will be created for the items you have marked to be invoiced.
Kind regards,
Leslie