There is no single official average rent increase for Dublin, and advertised market rents are not the same as increases for existing tenants. The amount a landlord may charge depends on the tenancy date, property, previous rent and rent-control rules applying at the time. In general, rent cannot be increased more than once in 12 months, and any applicable statutory cap must be observed, subject to limited exceptions. Check the RTB and gov.ie for the current rules; whether a particular increase is valid ultimately depends on the tenancy’s facts.