In a Rent Pressure Zone, the permitted increase is generally the lower of 2% or the rate of inflation measured by the Harmonised Index of Consumer Prices (HICP), using the figures and dates specified by the RTB. The lower percentage is applied to the current lawful rent to calculate the maximum new rent, rather than to an estimate of the property's market value. Rent can normally be reviewed only once every 12 months and the required notice must be given. Check the RTB rent calculator and current government guidance, as rules, dates and exemptions can affect the calculation.