If you are looking at setting up workflow to use with accounts payable invoices then you might want to consider the effect of putting the posting step before or after the approval step.
This will depend how you want to manage your business process. For example if the post is after the approval then the invoice won’t have hit the vendors account or the GL as it will be a pending invoice. If the post is before the approval then the invoice will be an open invoice and be in the GL and then you can approve later.
If you do want to approve after the post you might want to have a look at hiding the invoice from the payment until it is approved. You can see the approved flag in this post. or put the invoice on hold.
Here is a quick overview.
AX2012 R3 CU11