Iran’s official currency is Rial. However you will see and hear Toman a lot more commonly in the country.
Toman is one tenth of a Rial. So when purchasing, if someone quotes 23000 Toman (or 23 Toman), it works out to be 230,000 Rial.
Most prices written on the items in the bazaars, stores, or restaurants are in Toman but before you pay if you are not sure ask the shopkeeper whether the price is in Rial or Toman.
The tourists who travel to Iran cannot use their Visa or Master card or to withdraw any cash from ATM machines in the country, because of sanctions still in place on banks of Iran. So the travelers must bring cash only for their entire stay. US dollars, Euros, and UK pound are the most preferred in Iran’s banks or the private exchange offices named Sarāfi. Other currencies can be exchanged as well but the named three are more common and have a better rate.
The Sarāfi offices offer you a better rate of exchange compare to the banks and you can find Sarāfis at the airports, large cities, and tourist centers.