The Referendum Commission has launched a campaign, urging people to ensure they are registered to vote in the upcoming referendum on blasphemy.
The vote is taking place on Friday, October 26, the same date as the presidential election.
People must register before October 9 to vote in the referendum and presidential election.
While the commission's remit only covers the referendum, it says being on the electoral register allows people to vote in both the referendum and the presidential election.
Chairperson of the Referendum Commission, Isobel Kennedy said: "If you are not sure whether you are registered to vote in the forthcoming referendum, or whether or not you are registered at the correct address, you can find out very simply by checking the electoral register at www.checktheregister.ie."
"You can also check the register in local authority offices, post offices, Garda stations and public libraries."
If you are not registered, you can make sure you are added to a supplement to the register by completing a form which you can download here, or obtain from your local authority, Garda station, post office or public library.
You can then bring the completed form to your local Garda station to have your identity certified, and ensure it gets to your local authority before October 9.
People ordinarily registered at a hospital, nursing home or similar institution who are unable to vote at a polling station can vote at their hospital or nursing home, but only if they register on the Special Voters list.
The closing date for this is October 1, and application forms are available from local authorities, libraries, post offices, Garda stations or online.
October 1 is also the deadline to apply for a postal vote.
These are available to certain people - including Irish diplomats and their families posted abroad, members of the Garda and Defence Forces, prisoners and others who are unable to vote at their local polling station because of their occupation, service or employment.
