Venezuela will replace its 100-bolivar banknotes with coins within 72 hours.
The government hopes swapping the country’s highest denomination notes will help to stop smuggling and tackle shortages of food and other items.
Venezuela’s President Nicolas Maduro says gangs operating in border areas will not have time to repatriate the notes.
Opposition leader Henrique Capriles tweeted: “When ineptitude governs! Who would possibly think of doing something like this in December amid all our problems?”
Others argued it would be impossible to swap all the 100-bolivar notes in circulation in the time allotted.
The 100-bolivar note has lost most of its value over the past few years and is now worth about 2 US cents.
Venezuela, which is facing a serious economic and political crisis, has one of the world’s highest inflation rates.
President Nicolas Maduro said on TV: “I have given the orders to close all land, maritime and air possibilities so those bills taken out can’t be returned and they’re stuck with their fraud abroad.”
Earlier this month, Venezuela’s central bank said that six new bills ranging from 500 to 20,000 bolivars would come into circulation on December 15.
The government last published figures for inflation in December 2015, putting it at 180%, but the IMF estimates that next year’s prices will rise by more than 2,000%.