A system that is transparent (for collections, not payments) is ideal. It makes cheating harder, even if it doesn't solve all ways of cheating. Untaxable money

A system that is transparent (for collections, not payments) is ideal. It makes cheating harder, even if it doesn't solve all ways of cheating. Untaxable money would make cheating easier for lack of accounting. An "exit for the minorities at the edges" will always exist by paying outside the system (possibly using a private/local currency.) In fact the exit will be easier to use and more beneficial for poorer people since they're dealing with smaller amounts in a local community of trust. Wealthy cheats who try to exit a system like this will loose the availability of a trusted money (a species) not controlled by governments.