In the United States, people cannot be placed in prison solely for financial debt. You can, however, be imprisoned for failing to appear at court proceedings or failure to attempt to pay fines or dues ordered by a court. For instance, if the judge orders you to pay damages in a judgment and you do not attempt to pay, you can be imprisoned for contempt of court.
In Great Britain, the Debtors Act of 1869 forbids imprisonment for those who do not have the means to pay off a debt.
Most countries are party to the International Covenant on Civil and Political Rights. It states, among other things, that “No one shall be imprisoned merely on the ground of inability to fulfill a contractual obligation.”