The moratorium on broadcast news outlets reporting on issues in the referendum has come into effect from 2pm.
Radio and television broadcasters are bound by rules prohibiting new stories, including breaking news stories, that influence or manipulate voters' decisions.
Reporting of basic facts such as the hours at which polls are open, turnout figures, and the voting of notable politicians is still permitted. The views of programme guests or arguments about the issues, however, are expected to be curtailed.
The ban applies only to broadcast media, and not to print newspapers or online outlets. The moratorium is part of the Broadcasting Authority of Ireland's code of practice relating to election coverage.