Just like _actual_ cash!
The bank doesn't scan the serial numbers on the money I deposit and yet they somehow correctly credit my account.
Cash counting machines in banks scan and record numbers to find bills that have already been flagged (such as those stolen from banks/ATMs), but that process is unrelated to the crediting of money to your account. General cash tracking is hypothetically possible, but it would not be trivial to implement.
Re:The Security Behind the Birth of Zcash
by valarauca1 on Sunday July 16, 2017 @11:41PM
(#14785498)
They actually do.
Well not _you_ but bills do get flagged if they're involved in crimes (like kidnapping or robbery). So when they're deposited in a bank the FBI can track the _relative_ location of criminals.
https://mobile.twitter.com/zooko/status/863506504518914050