6) - the "expired" cash is worth 40% less every two years ( so after 4y is worth 0.60.6 and so on ) , and the expiry date cannot be verified (only bank can veri

6) - the "expired" cash is worth 40% less every two years ( so after 4y is worth 0.60.6 and so on ) , and the expiry date cannot be verified (only bank can verify during a deposit ) but only validated during the taking in charge of the banknote during a transaction., only in this way this system work (otherwise a parallel market of expired currency could arise) ... you can build a blockchain around that system if you prefer :) :: PROBLEMS & SOLUTIONS :: 7 ) single-state database would be not enough .. because in Europe there is a single currency shared between more states.. this way new-entry of cash may seems expired.. in this case, however, until the system is implemented at European level it is possible to monitor the flow of "unregistered" cash that a merchant acquires during the activity, and still allow checks on individual cases that become suspect, or the merchant is required to verify the identity card of a foreigner who pays cash in excess of X, everything would still be very effective because the amounts collected in Italy in cash from a foreigner are traced at least in the receiving part and from there on money enters the validation round you can in the case put a limit on the cash-transaction ( credit card is ok ) used for foreign purchases in Italy with "expired" cash which is much more effective and less limiting than putting a low limit on all purchases in cash , this is a quite low limit anyway circulating with large amount cash ( expecially between countries ) is already forbidden and dangerous.. thank you everyone for your comments, [1] https://www.bloomberg.com/news/articles/2019-09-17/italy-weighs-penalty-on-cash-withdrawals-to-fight-tax-evasion https://www.bloomberg.com/news/articles/2019-09-17/italy-wei...