Currently to the ease of Iran travelers, all the nationals can get a 14 days extendible on-arrival visa. The nationals of USA, England, Canada, Colombia, Pakistan, Afghanistan, Iraq, Jordan, Bangladesh, and Somalia are excluded of this rule. To accomplish the process, simply fill out the visa form on www.evisa.ir, your invitation letter will be issued in 48 hours and subsequently sent to your email address. The visa will be stamped in your passport at the airport when you arrive to Iran.