Sweden is the leading example of a "cashless" economy. Currency in circulation has been steadily declining in recent years, reaching a low of SEK 68.9 billion on October 15, 2015. That amounts to SEK 7,153 (US$ 844) per person. (Coins add another SEK 5.3 billion in circulation.) New electronic payment systems are accelerating the move away from cash.
Note the requirement imposed on banks that still deal with cash. Any person conducting a cash transaction in such a bank will have to declare how he (she) acquired the notes and coins, and the bank in turn has to report the information to the police.
In comparison, the value of U.S. currency in circulation, $4,300 per person as of December 31, 2014, continues to rise each year (although more than half is estimated to be held abroad). In accordance with the Patriot Act, U.S. banks are required to report to the Department of Homeland Security all transactions exceeding $10,000, although some will report transactions exceeding $5,000.
Still, Americans are relatively free to conduct cash transactions between themselves and between themselves and financial institutions. Swedes are not. Welcome to the Scandinavian version of Brave New World.