Is there any Law or Regulation that makes it illegal to put cash into a Safe Deposit box? Thanks

Many currency collectors such as myself keep "cash" in their safe deposit box. No federal regulations, check your state.

I don't believe there are any laws or regulations that prohibit putting cash into a box. However, you may want to check your Safe Deposit Box contract. The contract normally outlines things that you can not put into a box. Additionally, you probably should check your state laws.

As the other stated - Safe Boxes are for keeping valuables safe & cash is a vaulable.
SO - it is not illegal, but is unusual and should cause you to look a little further to see if (given other facts) it rises to the level Suspicious and reportable.

and keep in mind...you have no business actually knowing what a customer does or does not have in their SD box.