https://www.occ.treas.gov/topics/supervision-and-examination...
Keep records of cash purchases of negotiable instruments, File reports of cash transactions exceeding $10,000 (daily aggregate amount), and Report suspicious activity that might signal criminal activity (e.g., money laundering, tax evasion)
If you do more than $10,000 in cash business/transactions, the bank will (must) file a report -- if you're deposit $8000 one day and $4000 the next day, the bank might be forced to consider it a single transaction for $12,000 -- and file a SAR.
There's fantastic reasons to keep this confidential -- Given that requirements to file are so broad, almost all of these are going to be normal business activity.