Central Banks considering a "Carry Tax" on cash.
Goodfriend’s idea was to insert magnetic strips into the bills. Each time the cash was returned to a bank, the money would be taxed at a pre-determined rate. That would discourage individuals from hoarding cash and remove one obstacle for central bankers in setting negative rates.
Trump’s Federal Reserve Pick Wants to Put Metal Chips in Cash to Track Every Dollar and Tax It
http://thefreethoughtproject.com/trumps-federal-reserve-track-cash/
Trump's next Fed pick in limbo for wrong reason
https://www.nasdaq.com/article/trumps-next-fed-pick-in-limbo-for-wrong-reason-20180220-01672