According to the regulations of the Iranian Ministry of Foreign Affairs (MFA), a Tourist visa is issued for foreign nationals who are interested to travel to Iran individually or with a group for the purpose of visiting Iran, or their friends and relatives. This visa is issued for a maximum stay of 30 days with option of Extensions in Iran. Iran visa remains valid for a period of 3 months from the date of issue in the passport.
Consulates need an Authorization Letter for e-visa(called Grant Notice of Iran Visa, Invitation Letter, Reference Number , Approval Number and Authorization Number) from the Ministry of Foreign Affairs in Tehran. Getting this authorization number is the most important step in Iran visa application and there is not much left when you have it. You will usually have your visa in 1 or 2 days, after having the authorization code.