Dennis Hastert aside, it shouldn't be a crime to take your own money out of the bank

[Jim Lane]

37. Your hypothetical isn't suspicious because it's a check.

A check or electronic transfer leaves a record. If the bank customer is up to something shady, the movement of the money can be documented. I don't think a bank would report the $20k deposit to any authorities. A friendly teller might, as a personal matter, say something like, "Hey, you got a new job?" but that's it.

If someone who had been depositing $1,000 cash every week suddenly started depositing $20,000 cash every week, that would be very different. The bank would certainly file a currency transaction report (CTR) on each deposit. I don't know the rules for filing a Suspicious Activity Report (SAR) but it wouldn't surprise me if someone at the bank noticed this very strange development and filed the SAR.

I also don't know what happens when the Treasury Department gets the CTR's. If someone who hasn't been on their radar at all is suddenly being CTR'd for $20k every week, presumably an alarm goes off and there's at least some sort of inquiry. It's not proof that the bank customer is committing a crime, but you'd have to figure that a high percentage of the people dealing with that much cash are selling drugs or running numbers or the like.