Demonetization is the act of stripping a currency unit of its status as legal tender. It occurs whenever there is a change of national currency: The current form or forms of money is or are pulled from circulation and retired, often to be replaced with new notes or coins.

https://en.wikipedia.org/wiki/Legal_tender#Demonetization

A famous example of demonetization occurred in 2016 when India demonetized 86% of its nation's currency.

Demonetization: Meaning, Example, and How It Works
https://www.investopedia.com/terms/d/demonetization.asp