Iran, The Law on the Presidential Election 1985, accessed 19 February 2020
Article 18 - Ministry of Interior, after counting the ballots inside and outside the country, must inform the public about the final results of the elections through mass media.
Article 19 - In every round of election, the qualified persons can only vote once upon presenting his or her birth certificate. Note - those qualified voters outside the country, can present their valid Iranian passport in case they lack their birth certificate.
IFES, Duality by Design: The Iranian Electoral System, March 2011, accessed 19 February 2020
“Out-of-country voting is mandated by law for referendums and takes place in Iranian consulates or embassies. Voters must present their passport as a means of identification. All the regulations outlined in the law apply to out of country voting, and the vote must take place on the same day as the referendum is held inside Iran. Important issues not outlined in the Referendum Act include the timing for a referendum, and regulations for the ballot text (the question put on the ballot paper).”
Al Jazeera website: 'Expats can vote in presidential elections but not in parliamentary elections or Experts Assembly elections that are based on electoral voting districts,'
International IDEA's Voting from Abroad Handbook