[Retric]

Banks report net transactions aka BoA and United have customers writhing checks back and forth all the time, but on a given day the net transaction is the sum of all those little transactions. Thus BoA would say the revived 1 million dollars net from United and united would say the lost 1 million to BoA. As long as those numbers match there is no reason not to trust them.

Cash is is handled separately and banks can slightly fudge those numbers. But, there digital cash on hand better match yesterday's balance plus today's net transactions.

PS: Banks can convert cash back and fort from digital to hard currency, but that's handeled by a third party which also reports those transactions.