Referendum posters have to be taken down today, or the campaign groups behind them could be fined.
From tomorrow, the Yes and No posters will be considered litter and will be subject to on-the-spot litter fines of €150.
It's the responsibility of each local authority to enforce the litter law.
It comes amidst calls to ban posters from all referendums in the future.
The Green Party spokesperson for local government, Councillor Malcolm Noonan, has said that the referendum exit polls showed that the poster campaign had little influence on voter attitudes or decision making.
"It is clear now that social media is the campaign tool of choice for elections and referenda.
"Posters are environmentally destructive, visually ugly and a waste of money; in the case of general elections, taxpayers money."
They want posters to be restricted by local authorities to designated sites in large towns or cities, where all campaigners and candidates can display their posters.