If you are one of Irans' lover and are enthusiast to visit this magnificent country, we have a good news for you that can alleviate tourists' concerns over US sanctions on individuals visiting Iran, Passports of travelers entering Iran will not being stamped. 
To counter US sanctions and ease the tourists' concerns, the passports of foreign tourists visiting Iran will not be stamped according to a bill which has been announced by Irans' president, Hassan Rouhani.

He's recently notified that with entry and exit stamps not to be put on the passports of the visiting tourists. Iran provides relevant policies after removing tourists' concerns about visiting Iran because of US sanctions. 

Recently Iran visa is a separated paper which offers to tourists. There will be no arrival and departure stamp on your passport. You just need to deliver the visa (on paper) to officer at immigration part at the time of departure from country.