An area may be designated as an RPZ where RTB Rent Index data shows annual rent inflation of 7% or more in at least four of the previous six quarters, and the area’s average rent for new tenancies is above the national average. The RTB assesses the data and may recommend designation to the Minister for Housing, who makes the formal decision. RPZ status is based on the prescribed statistical tests rather than simply on local concerns about high rents. Check the official gov.ie guidance for current designations and rules, as the legislation and criteria can change.