The effective devaluation of the Iranian rial comes as other proposals are being floated to boost commerce, including possibly waiving taxes for foreign companies.
Sanctions over Iran's nuclear program have hit the country's vital oil exports and blocked transactions on international banking networks. Inflation is running at more than 25 percent.
The central bank offered most importers an exchange rate of 24,779 rials for USD 1 today, a day after the official announcement. That compares with the previous government-set rate of 12,260 rials.