There are 2 types of Referenda:
When the government wishes to change something in the constitution it must hold a constitutional referendum.
When the government wishes to introduce a law of national importance the Seanad and Dail can petition the President to hold a referendum.
Who can vote In a Referendum?
Every Irish citizen who is 18 years and included in the register of electors is entitled to vote in a referendum.
Register of Electors
To find out if you are on the register of Electors go to www.checkthe register.ie
For any queries relating to registration change of address etc contact the Franchise Section your Local County Council.
List of County Councils http://www.housing.gov.ie/local-government/administration/local-authorities/local-authorities