Currency: The national currency of Iran is the Iranian Rial, although Iranians will often refer to the Toman, a unit of 10 Rials. It is nearly impossible to change Rials back into hard currency outside Iran, so try not to accumulate too many in your travels.
Credit Cards: No ATMs are available and credit cards are generally not accepted in shops and restaurants, although they may be in top-end shops and carpet dealers. Therefore you will need to be carrying cash when visiting. Do NOT take Travellers Cheques or cash passport cards as they are not possible to use in Iran.
All major currencies are exchangeable in the big cities although US dollars are more readily acceptable around the country. Euros are preferred in high denominations and notes printed after 1996 for US dollars.