Hi @tim2investcope   

If you are still looking for a solution that you described ie Company A creates an invoice and then an invoice is automatically created in Company B then we might have what you are looking for.  It is still in beta but Zed Axis Online is a way to to set up a connection and automated process .

You can check out the beta for Zed Axis Online here I would be very grateful for any feedback you have as we are rapidly evolving this solution for its official market release.

Zed