A landlord may refer to comparable local rents, improvements to the property, or increased running and maintenance costs when explaining an increase. However, these reasons do not automatically allow any amount: the landlord must follow the rent-control rules and any applicable cap, timing requirements and notice rules. The written notice should state the new rent and explain how it was calculated, with the required supporting details. If you believe the increase is invalid, check the current guidance on gov.ie or the RTB website and consider using the RTB dispute resolution process; the outcome depends on the facts of the tenancy.