As already mentioned in other topic, I really think this sync policy is an issue (syncing only in the background). Reason is simple - I make some changes on desktop, and then my wife opens the app somewhere in the store on her Android, and she doesn't see changes I did because the sync will happen only when she exits the app again...
It is a little hard to manage home finance like this if some user (my wife in this case) who is not technical person has to do some workarounds just to get the correct data.
My suggestion would be to make the sync on start as well as on exit. So when the app comes in the front automatic sync is triggered, and also like it is now, when it goes to the background... Another solution is to add somewhere big sync button visible (like in many apps) so that they can easily learn they need to press that, and it is visible as an reminder.