In Ireland, a landlord generally must give you at least 90 days’ written notice before a rent increase takes effect. The notice should state the new rent, the date it will start and the information used to calculate it, and a copy must usually be sent to the RTB on the same day. You should not have to pay the increased amount before the effective date. Rent increases are subject to statutory limits and rules, so check the current RTB guidance; any dispute is ultimately decided through the RTB process or by a solicitor.