Different companies have different procedures for how invoicing is done. Sometimes it done one by one for each order, sometimes is done at shipment and attached to the shipment. Their all dependent on the trade terms and relationships customer have with each other. AX is flexible in the options you have for invoicing. This example give a walk through of invoicing multiple delivered orders in an “invoice run” approach.
If you want to see the setup of the invoices before the process I covered that in this video.
This video was recorded with AX2012 R2 but the same concepts apply to any release of AX2012.