Quoting a relevant paragraph from the AML post above: Much like KYC, AML policies are recursive stochastic management of crime. The state deputizes financial institutions to, in effect, change the physics of money. In particular, it wants them to situationally repudiate the fungibility of money. (Fungibility is the property that $1 is $1 and, moreover, that you are utterly indifferent between particular dollars.) They are not required to catch every criminal moving money (that would not be a positive result!)