When trying to be able to add lines in the Address field of an Invoice, pressing ENTER simply doesn't work.  Neither does it help in Preferences to set Enter to change to a new field: that only takes you out of the field you are trying to add a line to! The only work-around I have found is to add spaces, then double check the print preview until Quickbooks (somewhat arbritrarily in my experience) "decides" that if there finally are enough spaces to create a new line. I would MUCH rather see Quickbooks allow Ctrl-Enter or Shift-Enter to create a new line in the Address field instead of this, but I've found nothing else that works.