It's been quite a while since we tried using those two together, but I recall having to have just one of the locations synced with Express Invoice. We made a location called "Sales" which was synced. We then had to transfer product from say "Warehouse Q" over to "Sales." We ended up giving up on trying to use them together. As much as we really really wanted it to work, it just could not be relied on to sync properly. Most of the time it would work, but once in a while it would glitch out and not sync something properly. Unless you're watching every little thing it does, you'd never know if it worked or not. We couldn't tolerate software that we couldn't trust to do it right. I often consider going back and trying it again, but I just don't know if I dare.