The Referendum Commission is urging people to check the register.
It has launched a public information campaign which will see impartial advice on the eighth amendment sent to more than two million homes in Ireland.
Labour leader Brendan Howlin says it is important people have their say.
"Check the register. Don't assume you are on it," advised Mr Howlin.
"Every single referendum, every single election we have in our offices' people who tell us that they turned up to vote, had been on the register previously and somehow, they have lost that right.
"So check the register now."
- Digital Desk