The number of landlords investigated over serious breaches of rental laws has doubled over the last year as the Residential Tenancies Board (RTB) cracks down on rent rises outside of Rent Pressure Zone rules.

The RTB started 249 new investigations into deliberate breaches of rental law so far in 2025, double the number (124) started in the whole of 2024.

The main driver of this significant increase in investigations was data received by the board at the end of 2024 which showed significant noncompliance with Rent Pressure Zone (RPZ) rules.

RPZ rules cap rent increases at 2 per cent per year, or the rate of inflation, whichever is lower. While previously only certain areas in the State came under RPZ rules, the whole country has been in a Rent Pressure Zone since June 2025.

The new data, collected by the RTB and analysed by the Economic and Social Research Institute (ESRI), identified 16,000 “tenancies of concern”, where landlords were found to have increased rents above the threshold allowed in RPZs.

This data, collected by the RTB and analysed by the Economic and Social Research Institute (ESRI), identified 16,000 “tenancies of concern”, where landlords were found to have increased rents above the 2 per cent threshold allowed in RPZs.

Following the analysis of this data, the RTB then began a compliance campaign targeting these landlords, asking them to correct their rent and return overpaid rent to tenants.

Where this did not work, the board then brought these cases into its investigations process.

The figures were outlined by the RTB at its quarterly update for Q3 2025 on Thursday morning. The ESRI also provided an updated Rent Index for the first quarter of this year.

Speaking about the compliance process at the launch, RTB director Rosemary Steen said “both tenants and landlords need to understand that it isn’t a free for all and they must co-operate with the regime that is in place and the legislation that was passed.

“It’s a national requirement, and we intend to oversee that extremely diligently,” Ms Steen said.

Meanwhile, the latest figures from the rent index show average rents for new tenancies rose by 5.5 per cent annually to €1,696 in the first quarter of this year, with existing tenancies increasing by 4.4 per cent to €1,452.

The rate of inflation varied significantly across the regions, with Dublin seeing its lowest new tenancy growth rate since 2022 at 3.3 per cent in Q1 2025 – now €2,143 per month on average.

However, counties Donegal, Kerry, Kildare, Laois, Limerick, Monaghan, Roscommon and Tipperary saw increases in new tenancy rents of more than 10 per cent, something the RTB said is concerning.

While many of those counties were outside of Rent Pressure Zone rules at the time the data was collected, the RTB will now be running an information campaign in these areas to ensure landlords and tenants know the entire country is now under RPZ rules.

The new data also shows the number of tenancies continues to rise, and is up 3.2 per cent over the last year to a total of 240,798 in Q2 2025.

This is an increase of just less than one per cent since Q1 2025.

Large institutional landlords with more than 100 tenancies continue to make up a significant share of the market.

The proportion of tenancies provided by landlords with more than 100 tenancies has increased for eight consecutive quarters and now stands at 13.9 per cent, up from 11.8 per cent one year ago.

Similarly, the number of approved housing body registered tenancies grew by 11.7 per cent annually to 52,989.

The number of notices of termination received by the RTB has increased significantly year on year, up 17 per cent since this time last year but just less than 1 per cent higher than the last quarter, with a total of 4,728 received.