“Many commentators have noted that mainstream economists are calling to do away with cash entirely. It would be easy to scoff at these proposals as completely insane if the Fed hadn’t published a paper back in 1999 suggesting the implementation of a ‘carry tax’ or taxing actual physical cash using an expiration date if depositors aren’t willing to spend the money. The author of this lunacy is a visiting scholar with the ECB, the Fed, the IMF, and the Swiss National Bank. The fact that two of those groups have already imposed negative interest rates (ECB and SNB) should give warning that these sorts of ideas are actually taken very seriously by Central Banks.”
http://www.zerohedge.com/news/2015-05-16/secret-fed-paper-advocated-carry-tax-all-physical-cash