Fed Chairman Jerome Powell pointed to those left behind as evidence that the economic recovery is still not complete.
The IMF has been calling for a minimum global corporate income-tax rate.
Extreme poverty is set to rise for the first time in more than two decades, the IMF said.
The extra $400 unemployment payments will probably last only a month, Goldman Sachs economists said.
The estimate is based on a five-month school closure, the World Bank said in a report.
Severe climate events may impact companies owning assets in areas hit by drought, floods, wildfires and storms, the fund said.
The IMF estimates that global gross domestic product will shrink 3% this year.
Treasuries resumed rising and stocks pared losses after the surprise announcement.
The ongoing drama could take time to either play out or blow up.