For an RPZ tenancy, the permitted increase is generally calculated by applying the lower of the relevant inflation rate or the legal percentage cap to the existing rent, with any required pro-rating. For example, if the rent is €1,500 a month and the applicable HICP rate is 1.5%, the increase is €22.50 (€1,500 × 1.5%), making the new rent €1,522.50. This assumes the tenancy is eligible and a review is permitted at that time. Check the RTB’s current guidance and calculator, as rules, caps and exemptions can change.