Tehran has been planning since 2008 to redenominate the national currency as it continued devaluation. Now, the government is pushing the plan forward following the drastic loss of the currency value in 2018 after the restoration of economic sanctions on Tehran in 2018.
The idea was floated in 2008 under the previous administration of President Mahmoud Ahmadinejad but didnt move forward. The current situation with recent rial devaluation has spurred authorities to push it forward.