If the reference field were pre-filled with the previous reference, but already ‘selected’ when you tapped on it, then for those who want to change the reference, there’s no extra step (tap on the field, start typing, it will erase the previous reference). This is, for instance, how the system search on iOS works (pull down the screen, last search pre-populated but selected, so you can just type over it).
Regarding the listing order, I’d like to see a combination. Say, top 5 being my most recent payees, sorted by date, dividing line, then the full alphabetical list of previous payees.
One feature not mentioned, but necessary for the full CA, is the ability to remove payees from the list.
Thanks for sharing this!