I worked in a bank for a bit. Literally any transaction that’s large and unusual for the account will be flagged. Also people do bonkers things with their money for the stupidest reasons all the time so all that one has to do if they’re making large transactions is be prepared to talk to the bank and explain what’s going on.

Unless of course you are handling money in relation to organized crime, in which case you were fucked the moment the money touched the banking system