1) Demonetise 2) Deprive of value for payment 3) Devaluate 4) Devalue 1) Demonetise 
• (v. t.) To deprive of current value; to withdraw from use, as money.
To officially decide that a particular coin or banknote can no longer be used as currency
De·mon'e·tize transitive verb To deprive of current value; to withdraw from use, as money. « They [ gold mohurs] have been completely demonetized by the [ East India] Company.» R. Cobden. 
[v] - deprive of value for payment
demonetize, demonetise (British) 1. To stop using a particular metal to make coins. 2. To withdraw units of money from circulation. 3. To deprive (an issue of postage stamps) of validity by legal methods and without marking the stamps themselves.
demonetise verb deprive of value for payment; `demonetize a coin`
to divest (a monetary standard or the like) of value. · to withdraw (money or the like) from use. · to deprive (an issue of postage stamps) of validity by legal methods and without marking the stamps themselves.