One of the reasons why the US dollar remains the reserve currency is because it has NEVER been canceled. Europe routinely cancels coins and banknotes to prevent people from hiding cash. British is canceling the outstanding old paper banknotes of the 20 and 50-pound notes. They did issue polymer notes which are still valid – for now. This is how Europe will also force Digital Currency by eventually canceling all paper money forcing the underground economy to seek other methods.