Which governments force people to accept and use their currency?
The US government and most other Western governments, impose their currencies whenever there are transactions with the government. You typically have you pay your taxes in the national currency. Likewise, the government will pay its employees in the local currency, it will pay its debts in its currency, and when it exercises eminent domain, it can force you to take currency in exchange for property.
If you look at a dollar bill, it says “this note is legal tender for all debts, public and private.” As you note, you can contract to be paid in anything you like, but that only gets you so far. When there is a debt, the debtor has the right to pay in dollars. This limits your ability to opt out of the national currency. If you go to court in the US to enforce a contract, the court won’t typically require “specific performance”—instead, the court will impose money damages, which are a debt, payable in dollars. You can agree to pay the plumber in silver, but if you don’t, the plumber will have to accept dollars.
The US government and most other Western governments, impose their currencies whenever there are transactions with the government. You typically have you pay your taxes in the national currency. Likewise, the government will pay its employees in the local currency, it will pay its debts in its currency, and when it exercises eminent domain, it can force you to take currency in exchange for property.
If you look at a dollar bill, it says “this note is legal tender for all debts, public and private.” As you note, you can contract to be paid in anything you like, but that only gets you so far. When there is a debt, the debtor has the right to pay in dollars. This limits your ability to opt out of the national currency. If you go to court in the US to enforce a contract, the court won’t typically require “specific performance”—instead, the court will impose money damages, which are a debt, payable in dollars. You can agree to pay the plumber in silver, but if you don’t, the plumber will have to accept dollars.