That is what I was wondering. Can the government simply cancel the currency, or would that cause a bunch of other problems?
It would certainly cause some short-term problems, but I think it be better off in the long run.
I remember reading about these German bank robbers who made off with about $10 million Germen dollars, or whatever the German currency is called. They refused to disclose where they hid it because they knew once they got out they’d be relatively well-off men for the rest of their days. So they pled guilty and accepted their sentences.
While they were serving their sentence, the German government changed its currency and gave the population about a year to take their money to the bank for the new currency, after which time the old currency would become worthless pieces of paper.
The robbers, for their trouble ended up with nothing in the end.