If you believe an RPZ rent increase is too high or the rent review notice is invalid, you can refer a rent review dispute to the Residential Tenancies Board (RTB). Keep the notice, tenancy agreement, payment records and any evidence about the property’s previous rent, and check the current referral deadline with the RTB. Avoid withholding rent without advice; continue paying the existing or otherwise undisputed amount while the matter is being considered. The RTB will assess the individual tenancy and decide the dispute, so check the latest RPZ rules on RTB.ie or the official government website, or speak to a solicitor if the amount is significant.