[jasomill]

As someone who's had to dispute NSF charges for reordered transactions, I question the author's claim that ATM operations commute. Specifically, assume a $0 beginning balance. Then "withdraw $20 then deposit $200" might yield an error, $0 cash, and a $200 balance where "deposit $200 then withdraw $20" would net $20 cash and a $180 balance.

Or, as in my disputed case, $20 cash and a $140 balance, because the deposited check hadn't actually cleared by close-of-business, so end-of-day processing assessed a $40 negative balance fee despite the fact that the deposit "eventually" cleared. The first manager I discussed this with had the audacity to claim it was my fault for not somehow recognizing that the portion of the deposited funds the ATM made available for immediate withdrawal by design were not, in fact, available for immediate withdrawal.